JP2000244070A - Semiconductor device and semiconductor light emitting element - Google Patents

Abstract

(57) Abstract: In a semiconductor device or a semiconductor light emitting device having a heterointerface where two different nitride-based III-V compound semiconductor layers are in contact with each other and a band discontinuity exists,
A current is made to flow easily across the hetero interface, and the conductivity is improved. SOLUTION: Two different nitride-based III-V are provided.
In a semiconductor device or a semiconductor light-emitting element having a heterointerface where a group III compound semiconductor layer is in contact and a band discontinuity exists, a superlattice layer or a composition gradient layer that pseudo-eliminates or reduces band discontinuity is inserted at the heterointerface. I do. G
In the aN-based semiconductor laser, n-type Al is formed at a hetero interface between the n-type GaN contact layer 4 and the n-type AlGaN cladding layer 6.
The GaN / GaN superlattice layer 5 or the n-type AlGaN graded layer is inserted, and the p-type AlGaN cladding layer 11 and the p-type
The GaN / GaN superlattice layer 12 or the p-type AlGaN graded layer is inserted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a semiconductor light emitting device, and more particularly to a semiconductor device and a semiconductor light emitting diode using a nitride III-V compound semiconductor, which are suitably applied to a light emitting diode or an electron transit device. is there.

[0002]

2. Description of the Related Art In recent years, nitrides such as AlGaInN
2. Description of the Related Art Semiconductor light emitting devices such as semiconductor lasers and light emitting diodes that can emit light in the visible region to the ultraviolet region using II-V group compound semiconductors have been actively developed. Of these, light emitting diodes have already been put to practical use. Efforts have been made to extend the life of semiconductor lasers after room-temperature continuous oscillation has been achieved, but they have not yet been put to practical use. In particular, in the field of optical recording, this semiconductor laser is expected to be put to practical use as a semiconductor laser that can emit light in a short wavelength range in order to improve the recording density of an optical disk or the like.

FIG. 11 shows an example of a conventional GaN-based semiconductor laser. This GaN-based semiconductor laser is SCH (Sepa
Rate Confinement Heterostructure).

As shown in FIG. 11, in this conventional GaN-based semiconductor laser, a GaN buffer layer 102 and an undoped GaN layer 10 are provided on a c-plane sapphire substrate 101.
3, n-type GaN contact layer 104, n-type AlGaN cladding layer 105, n-type GaN optical waveguide layer 106, Ga _1-x
An active layer 107 having an In _x N / Ga _1-y In _y N multiple quantum well (MQW) structure, a p-type AlGaN cap layer 108,
A p-type GaN optical waveguide layer 109, a p-type AlGaN cladding layer 110, and a p-type GaN contact layer 111 are sequentially stacked. an upper layer portion of the n-type GaN contact layer 104,
n-type AlGaN cladding layer 105, n-type GaN optical waveguide layer 106, active layer 107, p-type AlGaN cap layer 10
8. The p-type GaN optical waveguide layer 109 and the p-type AlGaN cladding layer 110 have a predetermined mesa shape. Further, the upper layer of the p-type AlGaN cladding layer 110 and the p-type GaN
The contact layer 111 has a ridge shape extending in a stripe shape in one direction. Then, the p-type GaN of this ridge portion
The p-side electrode 112 is in ohmic contact with the contact layer 111, and the n-type Ga
The n-side electrode 113 is in ohmic contact with the N-contact layer 104.

[0005]

However, the above-mentioned conventional GaN-based semiconductor laser has a considerably high operating voltage as compared with a GaAs-based semiconductor laser which has been widely used, and has a practical problem. In addition, such a high operating voltage not only shortens the life of the GaN-based semiconductor laser, but also hinders an increase in output, and therefore, a reduction in the output has been strongly desired.

Accordingly, the present invention relates to a nitride III
It is an object of the present invention to reduce the operating voltage of a semiconductor light emitting device using a group V compound semiconductor.

The present invention more generally relates to two nitride-based III-V compound semiconductor layers different from each other,
In a semiconductor device having at least one heterointerface having band discontinuity and flowing a current across the heterointerface, an object of the present invention is to facilitate the flow of the current and improve conductivity.

[0008]

One of the reasons why the operating voltage of the above-mentioned conventional GaN-based semiconductor laser is high is that a p-type AlG
Heterointerface between aN cladding layer 110 and p-type GaN contact layer 11 and n-type GaN contact layer 105 and n
There is a large band discontinuity at the hetero interface with the AlGaN cladding layer 105, which may be an obstacle to a current flowing during laser operation and may deteriorate conductivity.

[0009] This problem can be effectively solved by inserting a layer which pseudo-eliminates or reduces band discontinuity at those hetero interfaces. And, as such a layer, a superlattice layer or a composition gradient layer can be used.

That is, in order to solve the above-mentioned problems, a first invention of the present invention provides two different nitride-based I-types.
In a semiconductor device in which a II-V compound semiconductor layer is in contact and has at least one heterointerface where a band discontinuity exists, a superlattice layer which pseudo-eliminates or reduces band discontinuity is inserted at the heterointerface. It is characterized by the following.

According to a second aspect of the present invention, there is provided a semiconductor device in which two different nitride-based III-V compound semiconductor layers are in contact with each other and have at least one heterointerface having band discontinuity. It is characterized in that a composition gradient layer for pseudo-elimination or reduction of band discontinuity is inserted.

According to a third aspect of the present invention, there is provided a semiconductor light emitting device in which two different nitride-based III-V compound semiconductor layers are in contact with each other and have at least one heterointerface having band discontinuity. And a superlattice layer for pseudo-elimination or reduction of band discontinuity is inserted.

According to a fourth aspect of the present invention, there is provided a semiconductor light emitting device in which two different nitride-based III-V compound semiconductor layers are in contact with each other and have at least one heterointerface having band discontinuity. , Characterized in that a composition gradient layer for pseudo-elimination or reduction of band discontinuity is inserted.

In the present invention, nitride-based III-V compound semiconductors generally include gallium (Ga), aluminum (Al), indium (In), and boron (B).
And thallium (Tl), and at least one group III element selected from the group consisting of: and thallium (Tl), and a group V element containing at least nitrogen (N) and optionally further containing arsenic (As) or phosphorus (P). This nitride III
Some specific examples of -V group compound semiconductors include Ga
N, AlGaN, AlN, GaInN, AlGaIn
N, InN and the like.

In the first and third aspects of the present invention, for example, the superlattice layer has a different first nitride-based I
II-V compound semiconductor layer and second nitride III
-Having a structure in which Group V compound semiconductor layers are alternately stacked;
The thicknesses of the first nitride III-V compound semiconductor layer and the second nitride III-V compound semiconductor layer are set in a range where a tunnel effect occurs. Here, one of the first nitride III-V compound semiconductor layer and the second nitride III-V compound semiconductor layer constitutes a well layer, and the other constitutes a barrier layer. Alternatively, the superlattice layer has a structure in which first nitride III-V compound semiconductor layers and second nitride III-V compound semiconductor layers different from each other are alternately stacked, and The thickness of the well layer changes monotonically in the stacking direction (such a superlattice layer is called an inclined superlattice layer). Here, the change in the thickness of the well layer of the superlattice layer is, specifically, a quantum level formed in the well layer of each period of the superlattice layer during operation of the semiconductor device or the semiconductor light emitting element. Typically, for example, the energy of the first quantum level increases or decreases stepwise and monotonically in the stacking direction, so that the first nitride III-V compound semiconductor layer and the second nitride III Dividing the band discontinuity between the group-V compound semiconductor layers and taking energy close to each other, via these quantum levels, the first nitride-based group III-V compound semiconductor layer and the second nitride The holes or electrons are set such that holes or electrons can move by resonance tunneling between the valence band or the conduction band of the compound III-V compound semiconductor layer. First nitride system I
II-V compound semiconductor layer and second nitride III
The thickness of the -V compound semiconductor layer is generally 50 nm or less.

In the first and third aspects of the present invention, typically, the two nitride-based III-V compound semiconductor layers are B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layer ( However, 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦
1) and a B _x2 Al _{y2 Gaz2} In _1-x2-y2-z2 N layer (where 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦)
Consists of one), the superlattice layer B _x3 Al _y3 Ga _z3 In
_1-x3-y3-z3 N layer (however, 0 ≦ x3, y3, z3 ≦ 1,
x3 + y3 + z3 ≦ 1) and B _x4 Al _y4 Ga _z4 In
_1-x4-y4-z4 N layer (however, 0 ≦ x4, y4, z4 ≦ 1,
x4 + y4 + z4 ≦ 1) are alternately stacked. The thickness of these _{B x3 Al y3 Ga z3 In 1} -x3-y3-z3 N layer and _{B x4 Al y4 Ga z4 In 1} -x4-y4-z4 N layer is set to a range tunnel effect occurs. Alternatively, the thickness of the well layer of the superlattice layer monotonically changes in the laminating direction.

In the second and fourth aspects of the present invention, typically, the two nitride-based III-V compound semiconductor layers are formed of a B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layer ( However, 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦
1) and _{B x2 Al y2 Ga z2 In 1-} x2-y2-z2 N layer (where, 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦
Consists of one), the compositional gradation layer B _x5 Al _y5 Ga _z5 In
_1-x5-y5-z5 N layer (however, 0 ≦ x5, y5, z5 ≦ 1,
x5 + y5 + z5 ≦ 1). _{B x5 Al y5 Ga z5 In 1} -x5-y5-z5 N layer that constitutes the composition gradient layer is _{typically, B x1 Al y1 Ga z1 In} 1-x1-y1-z1 N layer and B _x2 A
_{l y2 Ga z2 In 1-x2} -y2-z2 -valent N layer electronic band or changing the composition to continuously connect the conduction band.

In the present invention, typically, the hetero interface is a hetero interface between the AlGaN layer and the GaN layer, and the super lattice layer or the composition gradient layer is inserted into the hetero interface. However, if the Al composition of the AlGaN layer is p, 0 <p ≦ 1. More specifically, for example, Ga
In the case of a semiconductor light emitting device such as an N-based semiconductor laser,
It has a structure in which a p-type AlGaN cladding layer and a p-type GaN contact layer are in contact with each other, and a p-type AlGaN cladding layer and a p-type AlGaN
Having a structure in which layers and p-type GaN layers are alternately stacked,
A superlattice layer in which the thickness of the p-type AlGaN layer and the p-type GaN layer is set to a range where a tunnel effect occurs, or a structure in which the p-type AlGaN layer and the p-type GaN layer are alternately stacked; The thickness of the p-type GaN layer is p-type AlG
a superlattice layer monotonically increasing in the stacking direction from the aN cladding layer toward the p-type GaN contact layer, or p-type A
A composition gradient layer composed of p-type AlGaN (where 0 ≦ q ≦ 1 where Al composition is q) that continuously connects the valence band of the lGaN cladding layer and the valence band of the p-type GaN contact layer is inserted. Is done. Further, the semiconductor light emitting device has, for example, a structure in which an n-type GaN contact layer and an n-type AlGaN cladding layer are in contact with each other.
N-type AlG at the hetero interface with the AlGaN cladding layer
a superlattice layer having a structure in which an aN layer and an n-type GaN layer are alternately stacked, and the thickness of the n-type AlGaN layer and the n-type GaN layer is set to a range in which a tunnel effect occurs;
Alternatively, it has a structure in which an n-type AlGaN layer and an n-type GaN layer are alternately stacked, and the thickness of the n-type GaN layer is n-type G
a superlattice layer monotonically reduced in the stacking direction from the aN contact layer toward the n-type AlGaN cladding layer, or n
N-type AlGaN (where, where Al is r, 0 ≦ r ≦ 1) that continuously connects the conduction band of the n-type GaN contact layer and the conduction band of the n-type AlGaN cladding layer is inserted. You.

In the present invention configured as described above, two different nitride-based III-V compound semiconductor layers are in contact with each other, and at the hetero interface where band discontinuity exists,
By inserting a superlattice layer or a composition gradient layer that pseudo-eliminates or reduces band discontinuity, current easily flows across the hetero interface, and conductivity is improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 1 shows a G according to a first embodiment of the present invention.
1 shows an aN-based semiconductor laser. This GaN-based semiconductor laser has an SCH structure.

As shown in FIG. 1, in the GaN semiconductor laser according to the first embodiment, on a c-plane sapphire substrate 1, a GaN buffer layer 2, an undoped GaN layer 3, an n-type GaN contact layer 4, n Type AlGaN / Ga
N superlattice layer 5, n-type AlGaN cladding layer 6, n-type Ga
N optical waveguide layer _{7, Ga 1-x In x} N / Ga 1-y In y NM
QW structure active layer 8, p-type AlGaN cap layer 9, p
-Type GaN optical waveguide layer 10, p-type AlGaN cladding layer 1
1. p-type AlGaN / GaN superlattice layer 12 and p-type G
The aN contact layers 13 are sequentially stacked. In other words, in the GaN-based semiconductor laser according to the first embodiment, unlike the conventional GaN-based semiconductor laser, n
-Type GaN contact layer 4 and n-type AlGaN cladding layer 6
N-type AlGaN / GaN superlattice layer 5 is inserted at the hetero interface with
A p-type AlGaN / GaN superlattice layer 12 is inserted at the hetero interface between the first and p-type GaN contact layers 13. These n-type AlGaN / GaN superlattice layer 5 and p-type A
The details of the lGaN / GaN superlattice layer 12 will be described later. As an example of the thickness of these GaN-based semiconductor layers, the n-type AlGaN cladding layer 6 is 0.5 μm, the n-type GaN optical waveguide layer 7 is 0.1 μm, the p-type AlGaN cap layer 9 is 20 nm, and the p-type GaN The optical waveguide layer 10 has a thickness of 0.1 μm.
The m and p-type AlGaN cladding layers 11 are 0.5 μm, and the p-type GaN contact layers 12 are 0.5 μm. n-type Al
GaN clad layer 6 and p-type AlGaN clad layer 1
For example, each Al composition is 0.06 (6%).

Upper layer of n-type GaN contact layer 4, n-type AlGaN / GaN superlattice layer 5, n-type AlGaN cladding layer 6, n-type GaN optical waveguide layer 7, active layer 8, p-type AlG
The aN cap layer 9, the p-type GaN optical waveguide layer 10, and the p-type AlGaN cladding layer 11 have a predetermined mesa shape.
The upper layer of the p-type AlGaN cladding layer 110, the p-type AlGaN / GaN superlattice layer 12, and the p-type GaN contact layer 13 have a ridge shape extending in one direction in a stripe shape. The p-side electrode 14 is in ohmic contact with the p-type GaN contact layer 13 in the ridge portion, and the n-side electrode 15 is in ohmic contact with the n-type GaN contact layer 4 in a portion adjacent to the mesa portion. I have. Here, the p-side electrode 14 is made of, for example, a Ni / Pt / Au film, and the n-side electrode 15 is made of, for example, a Ti / Al / Pt / Au film.

FIG. 2A shows that a p-type AlGaN layer serving as a barrier layer and a p-type GaN layer serving as a well layer are alternately stacked, and the thicknesses of the p-type AlGaN layer and the p-type GaN layer are continuous in the stacking direction. 1 shows an example of the structure of a p-type AlGaN / GaN superlattice layer 12 which is changing in a dynamic manner. Further, FIG.
2A shows a valence band of the p-type AlGaN / GaN superlattice layer 12 and a portion in the vicinity thereof. As shown in FIGS. 2A and 2B, in this example, the p-type AlGaN / GaN superlattice layer 12 is
p-type Ga in the order toward the aN contact layer 13
The N layer and the p-type AlGaN layer are formed by alternately laminating eight periods, and the total thickness of the p-type GaN layer and the p-type AlGaN layer in each period is constant. The thickness of the p-type GaN layer in each period depends on the energy of the quantum level of holes formed in these p-type GaN layers, for example, the first quantum level (shown by a horizontal solid line in FIG. 2B). AlGaN cladding layer 11
The energy discontinuity of the valence band between the p-type GaN contact layer 13 and the p-type GaN contact layer 13 is substantially equally spaced, and the p-type AlGaN
The thickness is selected so as to decrease gradually in the direction from the cladding layer 11 to the p-type GaN contact layer 13. Specifically, the thickness of the p-type GaN layer is
When viewed in the direction from 1 to the p-type GaN contact layer 13, the order is 0.5 nm, 1 nm, 1.5 nm, 2.0 nm,
2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, and 4.5 nm, and the thickness of the p-type AlGaN layer is viewed from the p-type AlGaN cladding layer 11 toward the p-type GaN contact layer 13. 4.5 nm, 4 nm, 3.
5 nm, 3.0 nm, 2.5 nm, 2.0 nm, 1.5
nm, 1 nm and 0.5 nm. In addition,
The calculation is performed on the assumption that the energy discontinuity of the valence band between the p-type AlGaN cladding layer 11 and the p-type GaN contact layer 13 is 35 meV.

FIG. 3 shows GaN according to the first embodiment.
1 shows a valence band of a p-type AlGaN / GaN superlattice layer 12 and a portion in the vicinity thereof when a forward bias is applied during operation of a system semiconductor laser. In this case, p-side electrode 14
The holes injected into the p-type GaN contact layer 13 are p-type A
Through the p-type AlGaN / GaN superlattice layer 12 by resonance tunneling via quantum levels close to each other formed in the lGaN / GaN superlattice layer 12, the p-type AlGa
It moves to the N clad layer 11. Therefore, p-type AlGa
The discontinuity of the valence band existing at the hetero interface between the N cladding layer 11 and the p-type GaN contact layer 13 can be regarded as pseudo-disappearing.

FIG. 4A shows that an n-type AlGaN layer serving as a barrier layer and an n-type GaN layer serving as a well layer are alternately stacked, and the thicknesses of the n-type AlGaN layer and the n-type GaN layer are continuous in the stacking direction. An example of the structure of the n-type AlGaN / GaN superlattice layer 5, which is changing in a dynamic manner, is shown. FIG. 4B is a view similar to FIG.
2 shows the conduction band of the n-type AlGaN / GaN superlattice layer 5 shown in FIG. As shown in FIGS. 4A and 4B, in this example, the n-type AlGaN / GaN superlattice layer 5
Are n-type AlGaN layers and n-type AlGaN layers in order from the n-type GaN contact layer 4 toward the n-type AlGaN cladding layer 6.
Type GaN layer is alternately laminated for 8 periods,
The total thickness of the n-type AlGaN layer and the n-type GaN layer in each period is constant. The thickness of the n-type GaN layer in each period depends on the energy of the quantum level of electrons formed in the n-type GaN layer, for example, the energy of the first quantum level (shown by a horizontal solid line in FIG. 4B). Contact layer 4 and n-type AlGaN
The energy discontinuity of the conduction band with the cladding layer 6 is selected so as to be divided at substantially equal intervals, and to be higher in the direction from the n-type GaN contact layer 4 to the n-type AlGaN cladding layer 6. Specifically, the thickness of the n-type AlGaN layer is 0.5 nm, 1 nm in order from the n-type GaN contact layer 4 toward the p-type AlGaN cladding layer 6.
1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm,
Increased to 3.5 nm, 4.0 nm and 4.5 nm, and n
The thickness of the n-type GaN layer is 4.5 in the order from the n-type GaN contact layer 4 to the n-type AlGaN cladding layer 6.
nm, 4 nm, 3.5 nm, 3.0 nm, 2.5 nm,
It has decreased to 2.0 nm, 1.5 nm, 1 nm and 0.5 nm. Note that the n-type GaN contact layer 4 and the n-type A
The calculation is performed on the assumption that the energy discontinuity of the conduction band with the lGaN cladding layer 6 is 75 meV.

FIG. 5 shows GaN according to the first embodiment.
FIG. 4 shows a conduction band of the n-type AlGaN / GaN superlattice layer 5 and a portion in the vicinity thereof when a forward bias is applied during operation of a system semiconductor laser. In this case, n-type G
The electrons injected into the aN contact layer 4 are n-type AlGa
This n-type AlGa is formed by resonance tunneling through quantum levels close to each other formed in the N / GaN superlattice layer 5.
It moves to the n-type AlGaN cladding layer 6 through the N / GaN superlattice layer 5. Therefore, the n-type GaN contact layer 4
It can be considered that the discontinuity of the conduction band existing at the hetero interface between the n-type AlGaN cladding layer 6 and the n-type AlGaN cladding layer 6 has been pseudo-disappeared.

Next, a description will be given of a method of manufacturing the GaN-based semiconductor laser according to the first embodiment of the present invention configured as described above.

That is, the Ga according to the first embodiment is
In order to manufacture an N-based semiconductor laser, first, as shown in FIG. 1, a c-plane sapphire substrate 1 is prepared, and a GaN buffer having a thickness of, for example, 30 nm at a temperature of, for example, 520 ° C. by MOCVD, for example. Grow layer 2. The GaN buffer layer 2 is composed of a crystal layer that is close to amorphous and serves as a nucleus when an underlayer is grown thereon. In the growth of the GaN buffer layer 2, for example, trimethyl gallium ((CH ₃ ) ₃ G
a) Gas and ammonia (NH ₃ ) gas are used. Next, an undoped GaN layer 3 is grown on the GaN buffer layer 2 by, for example, MOCVD at a temperature of, for example, 1020 ° C.

Next, the n-type GaN contact layer 4, the n-type AlGaN / GaN superlattice layer 5, the n-type AlGaN cladding layer 6, the n-type GaN optical waveguide layer 7, Ga _1-x In _x N / G
a _1-y In _y N MQW structure active layer 8, p-type AlGa
N cap layer 9, p-type GaN optical waveguide layer 10, p-type AlG
An aN cladding layer 11, a p-type AlGaN / GaN superlattice layer 12, and a p-type GaN contact layer 13 are sequentially grown. Here, the n-type GaN contact layer 4, which is a layer containing no In, the n-type AlGaN / GaN superlattice layer 5, the n-type A
lGaN cladding layer 6, n-type GaN optical waveguide layer 7, p-type A
The growth temperature of the lGaN cap layer 9, the p-type GaN optical waveguide layer 10, the p-type AlGaN cladding layer 11, the p-type AlGaN / GaN superlattice layer 12, and the p-type GaN contact layer 13 is, for example, about 1000 ° C. and contains In. G that is
The growth temperature of _{a 1-x In x N /} Ga 1-y In y N MQW structure of the active layer 8 is for example a 700 to 800 ° C.. In addition, the raw materials for growing these GaN-based semiconductor layers include, for example,
As a Ga raw material, trimethylgallium ((CH ₃ ) ₃ G
a), Trimethyl aluminum ((C
H ₃ ) ₃ Al), trimethyl indium ((CH ₃ ) ₃ In) as an In material, and ammonia (NH ₃ ) as an N material. As the carrier gas, for example, a mixed gas of hydrogen (H ₂ ) and nitrogen (N ₂ ) is used. As the dopant, for example, monosilane (SiH ₄ ) is used as an n-type dopant, and, for example, cyclopentadienyl magnesium (Cp ₂ Mg) is used as a p-type dopant. Particularly, when growing the n-type AlGaN / GaN superlattice layer 5 and the p-type AlGaN / GaN superlattice layer 12, the n-type AlGaN layer and the p-type AlGaN / GaN superlattice Lattice layer 1
For example, the growth rate of the p-type AlGaN layer that constitutes No. 2 is 1.
80 μm / h, n-type AlGaN / GaN superlattice layer 5
N-type GaN layer and p-type AlGaN / GaN constituting
The growth rate of the p-type GaN layer forming the superlattice layer 12 is a slightly lower growth rate, for example, 1.74 μm / h. Thereafter, the p-type AlGaN cap layer 9 and the p-type GaN
Optical waveguide layer 10, p-type AlGaN cladding layer 11, p-type A
A heat treatment for electrically activating the acceptors doped in the lGaN / GaN superlattice layer 12 and the p-type GaN contact layer 13 is performed. This heat treatment is performed, for example, using nitrogen (N ₂ ).
This is performed, for example, at about 700 ° C. in an atmosphere.

Next, a stripe-shaped resist pattern (not shown) having a predetermined width is formed on the p-type GaN contact layer 13.
After forming this, using this resist pattern as a mask,
For example, the ridge portion is formed by etching the p-type AlGaN cladding layer 11 to an intermediate depth in the thickness direction by a reactive ion etching (RIE) method. Thereafter, the resist pattern is removed.

Next, after forming a resist pattern (not shown) wider than the resist pattern used to form the ridge portion so as to cover the ridge portion, the resist pattern is used as a mask, for example, by RIE. The n-type GaN contact layer 4 is etched to an intermediate depth in the thickness direction to form a mesa. After that, the resist pattern is removed.

Next, a p-side electrode 1 made of, for example, a Ni / Pt / Au film is formed on the p-type GaN contact layer 13 in the ridge portion.
4 and an n-type G in a portion adjacent to the mesa portion.
On the aN contact layer 4, for example, Ti / Al / Pt / Au
An n-side electrode 15 made of a film is formed.

Thereafter, the c-plane sapphire substrate 1 on which the laser structure is formed as described above is processed into a bar shape by cleaving or the like to form both resonator end faces, and further, these resonator end faces are coated with end faces. After the application, the bar is cut into chips by cleavage. As described above, the intended GaN-based semiconductor laser having the SCH structure is manufactured.

As described above, according to the first embodiment, the n-type AlGaN / GaN superlattice layer 5 is inserted at the hetero interface between the n-type GaN contact layer 4 and the n-type AlGaN cladding layer 6. In addition, since the p-type AlGaN / GaN superlattice layer 12 is inserted at the hetero interface between the p-type AlGaN cladding layer 11 and the p-type GaN contact layer 13, the n-type GaN contact layer 4 and the n-type AlG
Discontinuity of conduction band existing at hetero interface with aN cladding layer 6 and p-type AlGaN cladding layer 11 and p-type GaN
The discontinuity of the valence band existing at the hetero interface with the contact layer 13 can be virtually eliminated. Therefore, when the GaN-based semiconductor laser operates, a current easily flows through these hetero interfaces, and the conductivity is improved. Thereby, the operating voltage of the GaN-based semiconductor laser can be significantly reduced. In addition, the life of the GaN-based semiconductor laser can be improved and the output can be increased by reducing the operating voltage.

Next, G according to the second embodiment of the present invention will be described.
The aN-based semiconductor laser will be described.

In the GaN-based semiconductor laser according to the second embodiment, similarly to the GaN-based semiconductor laser according to the first embodiment, the n-type GaN contact layer 4 and the n-type A
n-type AlGaN at the hetero interface with the lGaN cladding layer 6
/ GaN superlattice layer 5 is inserted and p-type A
lGaN cladding layer 11 and p-type GaN contact layer 13
P-type AlGaN / GaN superlattice layer 12
Are inserted, in this case, these n-type AlGa
In each of the N / GaN superlattice layer 5 and the p-type AlGaN / GaN superlattice layer 12, the thicknesses of the well layers and the barrier layers are set in a range where a tunnel effect occurs. Specifically, for example, as shown in FIGS. 6A and 6B, p-type A
The lGaN / GaN superlattice layer 12 is formed by alternately stacking eight p-type AlGaN layers and eight p-type GaN layers having a thickness at which a tunnel effect occurs, for example, a thickness of 50 nm or less, preferably 10 nm or less. It is constant. For example, as shown in FIGS. 7A and 7B, n-type AlGaN
The / GaN superlattice layer 5 is formed by alternately laminating an n-type AlGaN layer and an n-type GaN layer having a thickness at which a tunnel effect occurs, for example, 50 nm or less, preferably 10 nm or less, at eight periods, and each period is constant. It has become. Other points are the same as those of the first embodiment, and the description is omitted.

According to the second embodiment, similarly to the first embodiment, the n-type GaN contact layer 4 and the n-type AlG
n-type AlGaN / G at the hetero interface with the aN cladding layer 6
aN superlattice layer 5 is inserted and p-type AlG
Since the p-type AlGaN / GaN superlattice layer 12 is inserted at the hetero interface between the aN cladding layer 11 and the p-type GaN contact layer 13, the hetero interface between the n-type GaN contact layer 4 and the n-type AlGaN cladding layer 6 is obtained. And the discontinuity of the valence band existing at the hetero interface between the p-type AlGaN cladding layer 11 and the p-type GaN contact layer 13 can be virtually eliminated. Therefore, when the GaN-based semiconductor laser operates, a current easily flows through these hetero interfaces, and the conductivity is improved. Thereby, the operating voltage of the GaN-based semiconductor laser can be significantly reduced. In addition, the life of the GaN-based semiconductor laser can be improved and the output can be increased by reducing the operating voltage.

Next, G according to the third embodiment of the present invention will be described.
The aN-based semiconductor laser will be described. FIG. 8 shows this third
1 shows a GaN-based semiconductor laser according to the embodiment.

As shown in FIG. 8, in the GaN-based semiconductor laser according to the third embodiment, an n-type AlGaN graded layer 16 is provided at a hetero interface between the n-type GaN contact layer 4 and the n-type AlGaN cladding layer 6. The p-type AlGaN cladding layer 11 and the p-type G
p-type AlGaN at the hetero interface with the aN contact layer 13
The graded layer 17 is inserted. Here, the Al composition of the p-type AlGaN graded layer 17 is p-type A
1GaN cladding layer 11 to p-type GaN contact layer 1
3, the p-type AlGaN cladding layer 11
It decreases linearly from 1 composition (for example, 0.06) to 0. Therefore, as shown in FIG. 9B, p-type AlG
The valence bands of the aN cladding layer 11 and the p-type GaN contact layer 13 are continuously connected via a p-type AlGaN graded layer 17. Also, n-type AlGaN
The Al composition of the graded layer 16 linearly increases from 0 to the Al composition (for example, 0.06) of the n-type AlGaN cladding layer 6 in the direction from the n-type GaN contact layer 4 to the n-type AlGaN cladding layer 6. are doing. Therefore, as shown in FIG. 10B, the n-type GaN contact layer 4
The valence band of the n-type AlGaN cladding layer 6 is n-type A
They are continuously connected via an lGaN graded layer 17. Other points are the same as those of the first embodiment, and the description is omitted.

As described above, according to the third embodiment, the n-type AlGaN graded layer 16 is inserted at the hetero interface between the n-type GaN contact layer 4 and the n-type AlGaN cladding layer 6, and Since the p-type AlGaN graded layer 17 is inserted at the hetero interface between the p-type AlGaN cladding layer 11 and the p-type GaN contact layer 13, the n-type GaN contact layer 4 and the n-type Al
The discontinuity of the conduction band existing at the hetero interface with the GaN cladding layer 6 and the p-type AlGaN cladding layer 11 and the p-type Ga
The discontinuity of the valence band existing at the hetero interface with the N contact layer 13 can be pseudo-erased. Therefore, when the GaN-based semiconductor laser operates, a current easily flows through these hetero interfaces, and the conductivity is improved. Thereby, the operating voltage of the GaN-based semiconductor laser can be significantly reduced. In addition, the life of the GaN-based semiconductor laser can be improved and the output can be increased by reducing the operating voltage.

Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above embodiment, and various modifications based on the technical idea of the present invention are possible.

For example, the numerical values, structures, substrates, raw materials, processes, etc. described in the first to third embodiments are merely examples, and different numerical values, structures, substrates, raw materials, processes, etc. may be used as necessary. Or the like may be used.

More specifically, in the first to third embodiments, the case where the present invention is applied to a GaN-based semiconductor laser having an SCH structure has been described.
Needless to say, the present invention may be applied to a GaN-based semiconductor laser having a (Double Heterostructure) structure, and may be applied to a GaN-based light emitting diode.

In the first to third embodiments,
Although a c-plane sapphire substrate 1 is used as a substrate, generally, as a substrate of a semiconductor device or a semiconductor light emitting element, silicon carbide (SiC), zinc oxide (ZnO), spinel, silicon (Si), gallium arsenide ( GaAs) or the like may be used.

The nitride-based III-V compound semiconductor layer is grown by a method other than the MOCVD method, for example, a halide vapor phase epitaxial growth method (a chloride vapor phase epitaxial growth method is a kind) or a hydride vapor phase epitaxial growth method. (Both are referred to as “HVPE”), molecular beam epitaxy (MBE), or the like.

[0047]

As described above, according to the present invention, two different nitride-based III-V compound semiconductor layers are in contact with each other, and the hetero-interface at which band discontinuity exists exists.
By inserting a superlattice layer or a compositionally graded layer that pseudo-disappears or reduces the band discontinuity, current can easily flow across the hetero interface, and conductivity can be improved. In the semiconductor light emitting device, the operating voltage can be reduced, the life can be improved, and the output can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a GaN-based semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the GaN-based semiconductor laser according to the first embodiment of the present invention and a schematic diagram illustrating a valence band.

FIG. 3 is a schematic diagram illustrating a valence band when a forward bias is applied to the GaN-based semiconductor laser according to the first embodiment of the present invention;

FIG. 4 is a cross-sectional view of a main part of the GaN-based semiconductor laser according to the first embodiment of the present invention and a schematic diagram showing a conduction band.

FIG. 5 is a schematic diagram illustrating a conduction band of a main part when a forward bias is applied to the GaN-based semiconductor laser according to the first embodiment of the present invention;

FIG. 6 is a sectional view of a main part of a GaN-based semiconductor laser according to a second embodiment of the present invention and a schematic diagram showing a valence band.

7A and 7B are a cross-sectional view of a main part of a GaN-based semiconductor laser according to a second embodiment of the present invention and a schematic diagram showing a conduction band.

FIG. 8 is a sectional view showing a GaN-based semiconductor laser according to a third embodiment of the present invention.

FIG. 9 is a sectional view of a main part of a GaN-based semiconductor laser according to a third embodiment of the present invention and a schematic diagram showing a valence band.

FIG. 10 is a cross-sectional view of a main part of a GaN-based semiconductor laser according to a third embodiment of the present invention and a schematic diagram showing a conduction band.

FIG. 11 is a sectional view showing a conventional GaN-based semiconductor laser.

[Explanation of symbols]

1 ... c-plane sapphire substrate, 4 ... n-type GaN contact layer, 5 ... n-type AlGaN / GaN superlattice layer,
6 ... n-type AlGaN cladding layer, 7 ... n-type Ga
N optical waveguide layer, 8 ... active layer, 9 ... p-type AlGaN
Cap layer, 10 ... p-type GaN optical waveguide layer, 11 ...
-P-type AlGaN cladding layer, 12 ... p-type AlGa
N / GaN superlattice layer, 13 ... p-type GaN contact layer, 14 ... p-side electrode, 15 ... n-side electrode, 16 ...
..N-type AlGaN graded layer, 17 ... p-type AlGaN graded layer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masao Ikeda 7-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 5F041 AA24 AA44 CA04 CA05 CA34 CA40 CA46 CA65 CB05 5F073 AA13 AA45 AA74 BA06 CA07 CB05 CB09 CB10 DA05 EA28 EA29

Claims (26)

[Claims] 1. Two different nitride-based III-Vs
In a semiconductor device having at least one heterointerface where a group compound semiconductor layer is in contact and a band discontinuity exists, a superlattice layer for pseudo-eliminating or reducing the band discontinuity is inserted in the heterointerface. A semiconductor device characterized by the above-mentioned. 2. The superlattice layer is formed of a first nitride III-
It has a structure in which a group V compound semiconductor layer and a second nitride III-V compound semiconductor layer are alternately laminated, and the first nitride III-V compound semiconductor layer and the second nitride 2. The semiconductor device according to claim 1, wherein the thickness of the compound III-V compound semiconductor layer is set in a range where a tunnel effect occurs. 3. The superlattice layer is formed of a first nitride III-
It has a structure in which a group V compound semiconductor layer and a second nitride III-V compound semiconductor layer are alternately stacked, and the thickness of the well layer of the superlattice layer monotonically changes in the stacking direction. The semiconductor device according to claim 1, wherein: 4. The two nitride III-V group compound semiconductor layers are B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layers (where 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦).
1) and a B _x2 Al _{y2 Gaz2} In _1-x2-y2-z2 N layer (where 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦)
1), wherein the superlattice layer is B _x3 Al _{y3 Gaz3} In
_1-x3-y3-z3 N layer (however, 0 ≦ x3, y3, z3 ≦ 1,
x3 + y3 + z3 ≦ 1) and B _x4 Al _y4 Ga _z4 In
_1-x4-y4-z4 N layer (however, 0 ≦ x4, y4, z4 ≦ 1,
2. The semiconductor device according to claim 1, wherein (x4 + y4 + z4 ≦ 1) are alternately stacked. Wherein said _{B x3 Al y3 Ga z3 In 1} -x3-y3-z3 N
Layer and the _{B x4 Al y4 Ga z4 In 1} -x4-y4-z4 thickness of the N layer of the semiconductor device according to claim 4, characterized in that it is set in a range tunnel effect occurs. 6. The semiconductor device according to claim 4, wherein the thickness of the well layer of the superlattice layer monotonically changes in the stacking direction. 7. The method according to claim 1, wherein the hetero interface comprises an AlGaN layer and GaN.
2. The semiconductor device according to claim 1, wherein the semiconductor device is a hetero interface with a layer. 8. Two different nitride systems III-V
In a semiconductor device having at least one heterointerface where a group compound semiconductor layer is in contact and a band discontinuity is present, a composition gradient layer that pseudo-eliminates or reduces the band discontinuity is inserted at the heterointerface. A semiconductor device characterized by the above-mentioned. 9. The two nitride III-V group compound semiconductor layers are B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layers (where 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦).
1) and a B _x2 Al _{y2 Gaz2} In _1-x2-y2-z2 N layer (where 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦)
1), wherein the composition gradient layer is B _x5 Al _{y5 Gaz5} In.
_1-x5-y5-z5 N layer (however, 0 ≦ x5, y5, z5 ≦ 1,
9. The semiconductor device according to claim 8, wherein x5 + y5 + z5 ≦ 1). 10. The semiconductor device according to claim 1, wherein the heterointerface is formed of an AlGaN layer and Ga.
9. The semiconductor device according to claim 8, wherein the semiconductor device is a hetero interface with the N layer. 11. Two different nitrides III-
In a semiconductor light emitting device having at least one heterointerface in which a group V compound semiconductor layer is in contact with and having a band discontinuity, a superlattice layer that pseudo-eliminates or reduces the band discontinuity is inserted into the heterointerface. A semiconductor light-emitting device. 12. The superlattice layer is formed of a first nitride III
-V group compound semiconductor layer and second nitride III-V
The first nitride-based III-V compound semiconductor layer and the second nitride-based III-V compound semiconductor layer have a tunnel effect. 12. The semiconductor light-emitting device according to claim 11, wherein the range is set to occur. 13. The superlattice layer is formed of a first nitride III
-V group compound semiconductor layer and second nitride III-V
12. The semiconductor light emitting device according to claim 11, wherein the semiconductor light emitting device has a structure in which group compound semiconductor layers are alternately stacked, and the thickness of the well layer of the superlattice layer monotonically changes in the stacking direction. 14. The two nitride III-V compound semiconductor layers are B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layers (where 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦).
1) and a B _x2 Al _{y2 Gaz2} In _1-x2-y2-z2 N layer (where 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦)
1), wherein the superlattice layer is B _x3 Al _{y3 Gaz3} In
_1-x3-y3-z3 N layer (however, 0 ≦ x3, y3, z3 ≦ 1,
x3 + y3 + z3 ≦ 1) and B _x4 Al _y4 Ga _z4 In
_1-x4-y4-z4 N layer (however, 0 ≦ x4, y4, z4 ≦ 1,
12. The semiconductor light emitting device according to claim 11, wherein (x4 + y4 + z4 ≦ 1) are alternately stacked. 15. The B _x3 Al _{y3 Gaz3} In _1-x3-y3-z3
N layer and the _{B x4 Al y4 Ga z4 In 1} -x4-y4-z4 thickness of the N layer is a semiconductor light emitting device according to claim 14, wherein it is set to a range where the tunnel effect occurs. 16. The semiconductor light emitting device according to claim 14, wherein the thickness of the well layer of the superlattice layer monotonically changes in the laminating direction. 17. The method according to claim 17, wherein the hetero interface is formed of an AlGaN layer and Ga.
12. A hetero interface with an N layer.
The semiconductor light-emitting device according to claim 1. 18. A p-type AlGaN cladding layer and a p-type Ga
Having a structure in contact with an N-contact layer;
The superlattice layer having a structure in which a p-type AlGaN layer and a p-type GaN layer are alternately stacked is inserted at a hetero interface between the aN clad layer and the p-type GaN contact layer, and the p-type AlGaN layer and the The semiconductor light emitting device according to claim 11, wherein the thickness of the p-type GaN layer is set in a range where a tunnel effect occurs. 19. A p-type AlGaN cladding layer and a p-type Ga
Having a structure in contact with an N-contact layer;
The superlattice layer having a structure in which a p-type AlGaN layer and a p-type GaN layer are alternately stacked is inserted at a hetero interface between the aN clad layer and the p-type GaN contact layer, and the thickness of the p-type GaN layer is 12. The method according to claim 11, wherein the thickness monotonically increases in the stacking direction from the p-type AlGaN cladding layer toward the p-type GaN contact layer.
The semiconductor light-emitting device according to claim 1. 20. An n-type GaN contact layer and an n-type AlG
an n-type GaN having a structure in contact with an aN cladding layer;
The superlattice layer having a structure in which an n-type AlGaN layer and an n-type GaN layer are alternately laminated is inserted at a hetero interface between the contact layer and the n-type AlGaN cladding layer, and the n-type GaN contact layer and the n-type AlG
The semiconductor light emitting device according to claim 11, wherein the thickness of the aN cladding layer is set in a range where a tunnel effect occurs. 21. An n-type GaN contact layer and an n-type AlG
an n-type GaN having a structure in contact with an aN cladding layer;
The superlattice layer having a structure in which an n-type AlGaN layer and an n-type GaN layer are alternately stacked is inserted at a hetero interface between the contact layer and the n-type AlGaN cladding layer, and the thickness of the n-type GaN layer is 12. The method according to claim 11, wherein monotonically decreases from the n-type GaN contact layer toward the n-type AlGaN cladding layer in the stacking direction.
The semiconductor light-emitting device according to claim 1. 22. Two different nitrides III-
In a semiconductor light emitting device having at least one heterointerface in which a group V compound semiconductor layer is in contact and a band discontinuity is present, a composition gradient layer that pseudo-eliminates or reduces the band discontinuity is inserted into the heterointerface. A semiconductor light-emitting device. 23. The two nitride III-V compound semiconductor layers are B _x1 Al _{y1 Gaz1} In _1-x1-y1-z1 N layers (where 0 ≦ x1, y1, z1 ≦ 1, x1 + y1 + z1 ≦).
1) and a B _x2 Al _{y2 Gaz2} In _1-x2-y2-z2 N layer (where 0 ≦ x2, y2, z2 ≦ 1, x2 + y2 + z2 ≦)
1), wherein the composition gradient layer is B _x5 Al _{y5 Gaz5} In.
_1-x5-y5-z5 N layer (however, 0 ≦ x5, y5, z5 ≦ 1,
23. The semiconductor light emitting device according to claim 22, wherein x5 + y5 + z5 ≦ 1). 24. The heterointerface according to claim 1, wherein the AlGaN layer and the Ga
23. A hetero interface with an N layer.
The semiconductor light-emitting device according to claim 1. 25. A p-type AlGaN cladding layer and a p-type Ga
Having a structure in contact with an N-contact layer;
The above composition comprising p-type AlGaN which continuously connects a valence band of the p-type AlGaN cladding layer and a valence band of the p-type GaN contact layer at a hetero interface between the aN cladding layer and the p-type GaN contact layer. 23. The semiconductor light emitting device according to claim 22, wherein an inclined layer is inserted. 26. An n-type GaN contact layer and an n-type AlG
aN clad layer, and the n-type G
The composition gradient layer of n-type AlGaN that continuously connects a conduction band of the n-type GaN contact layer and a conduction band of the n-type AlGaN cladding layer at a hetero interface between the aN contact layer and the n-type AlGaN cladding layer. 23. The semiconductor light emitting device according to claim 22, wherein is inserted.