JP2002280673A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AlBGaInN-based semiconductor light emitting device having a configuration in which the uniformity of the In composition distribution of an active layer in a wafer surface is good. SOLUTION: This semiconductor light emitting device is made of Al _{x By y} Ga
_1-xyz In _z N (1> x ≧ 0, 1> y ≧ 0, and 1>
z> 0) -based semiconductor light emitting device having a single quantum well structure, in which GaN barrier layers 42A and 42B and GaN barrier layers 4
1 having an InN well layer 44 sandwiched between 2A and 2B.
An active layer having a single quantum well structure having a band structure as shown in FIG. Further, the present semiconductor light emitting device
In the example of the multiple quantum well structure, a band structure as shown in FIG. 1B having GaN barrier layers 46A to 46D and InN well layers 48A to 48C sandwiched between the barrier layers of the GaN barrier layers 46A to 46D, respectively. Of an active layer having a multiple quantum well structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an AlBGaInN
More specifically, the active layer In
The semiconductor laser device has a configuration with good uniformity of the composition distribution in the wafer surface, has a low threshold current value, has a large differential gain, and has a high color purity for a light emitting diode.
The present invention relates to a BGaInN-based semiconductor light emitting device.

[0002]

2. Description of the Related Art Ga on a sapphire substrate or a GaN substrate.
A GaN-based semiconductor laser device having a stacked structure of N-based compound semiconductor layers, in particular, an AlGaInN-based semiconductor laser device having a stacked structure of AlGaInN-based compound semiconductor layers emits light in a short wavelength range from blue to the ultraviolet region. As a semiconductor laser device.

Here, referring to FIG. 4, a conventional AlGa
The configuration of the InN-based semiconductor laser device will be described. FIG. 4 is a sectional view showing a configuration of a conventional AlGaInN-based semiconductor laser device. As shown in FIG. 4, a conventional AlGaInN-based semiconductor laser device 10 includes a c-plane sapphire substrate 12.
A first buffer layer 14 made of GaN grown at a low temperature, a second buffer layer 16 made of GaN, n-type GaN
A contact layer 18, a first cladding layer 20 made of n-type AlGaN, a first light guide layer 22 made of n-type GaN, G
a _1-x In _x N / Ga _1-y In _y N (x ≠ y) Active layer 24 having a multiple quantum well structure, second active layer having a p-type GaN
The light guide layer 26, the second clad layer 28 made of p-type AlGaN, and the p-type GaN contact layer 30 are sequentially stacked.

In the laminated structure, the upper layer of the n-type GaN contact layer 18, the first cladding layer 20, the first light guide layer 2
2. The active layer 24, the second light guide layer 26, the second cladding layer 28, and the contact layer 30 are formed as mesa portions extending in a predetermined direction.

On the contact layer 30, a p-side electrode 32 of a multilayer metal film such as a Ni / Au electrode is provided as an ohmic junction electrode, and on the n-type contact layer 18, like a Ti / Al electrode. N-side electrode 34 of simple multilayer metal film
Are provided as ohmic junction electrodes.

[0006]

However, the above-mentioned AlG
The active layer composed of a GaInN mixed crystal system generally used in an aInN-based semiconductor laser device has the following problems. That is, the miscibility difference between GaN and InN (mi
Due to the large scibility gap, for example, Mat.Res.Soc.S
As reported in ymp. Proc. vol. 482, 1998, p. 613, the active layer is likely to have a non-uniform In composition distribution. As a typical example of this inhomogeneity, the above-mentioned literature includes a quantum disk (Appl. Phys. Lett. Vol. 70,
1997, p. 981, reports that quantum dots (dots) are formed in the active layer.

In a semiconductor laser device, when such an uneven distribution of the In composition occurs in the active layer, it has been reported that the J.Selec.
As reported in t.Topics Quantum Elect. Vol. 4, 1998, p. 490, depending on the distribution of the non-uniform In composition, in a partial region within the wafer plane or in a local region. A semiconductor laser chip is formed in which the effective cavity length (cavity length) is short, the threshold current value is high, or the differential efficiency is low. That is, the laser characteristics vary within the wafer surface, and the product yield decreases.

By the way, Appl. Phys. Lett. Vol. 74, 1999,
As reported in p. 981, the greater the composition of In in the active layer, the greater the non-uniform distribution of the In composition. In other words, if an attempt is made to manufacture a light emitting element in a longer wavelength region by increasing the In composition, the fluctuation of the In composition becomes a more serious problem, leading to a reduction in product yield.

In the above problem, an AlGaInN-based semiconductor laser device is taken as an example.
This is a problem that also occurs in an nN-based semiconductor laser device. Furthermore, there is a problem that occurs not only in the semiconductor laser element but also in the AlBGaInN-based light emitting diode. For example, in a light emitting diode, if a non-uniform distribution of the In composition occurs in the active layer, the color purity of emitted light deteriorates.

It is an object of the present invention to provide an AlB having a structure in which the uniformity of the In composition distribution of the active layer in the wafer surface is excellent.
An object of the present invention is to provide a GaInN-based semiconductor light emitting device.

[0011]

As long as the active layer is a GaInN ternary mixed crystal, the difference in miscibility between GaN and InN causes fluctuations in the In composition in the active layer, and the above-mentioned problem is solved. Cause. Therefore, the present inventor has proposed that an active layer similar to a GaInN ternary mixed crystal active layer is formed by a quantum well structure including a binary InN well layer and a GaN barrier layer, and the thickness of the InN well layer is reduced. With the idea of controlling the quantum confinement effect by adjustment, the present invention has been made.

[0012] To achieve the above object, on the basis of the above findings, the semiconductor light emitting device according to the present _{invention, Al x B y Ga 1-} xyz In z N (1> x ≧ 0,1 having an active layer
> Y ≧ 0 and 1>z> 0) -based semiconductor light-emitting device, the active layer is formed by a quantum well of a barrier layer made of a group III binary group III nitride compound semiconductor other than In and a well layer made of InN. It is characterized by being formed as a well structure.

In the present invention, a group III binary group III nitride compound semiconductor layer other than In refers to GaN, AlN, and BN.
Etc., and is preferably a GaN layer.
The quantum well structure may be a single quantum well structure or a multiple quantum well structure. The present invention can be applied to an AlBGaInN-based semiconductor laser device and an AlBGaInN-based light emitting diode.

In the present invention, for example, a GaN barrier layer and InN
By forming a quantum well structure with a well layer and resembling a GaInN layer, an in-plane uniform GaInN
An active layer can be configured. That is, since the GaInN mixed crystal is not used for both the barrier layer and the well layer, G
Non-uniform fluctuation of the potential (band gap energy) due to fluctuation of the In composition in the aInN mixed crystal can be avoided. In addition, this makes it possible to lower the threshold current value of the semiconductor laser device and increase the differential gain. Further, the color purity of the light emitting diode can be increased.

By adjusting the well width of the well layer of the quantum well structure, as shown in FIG. 5, the emission energy (photon energy) inversely proportional to the wavelength is reduced from the ultraviolet region of less than 3.2 eV to less than 2.0 eV. It can be controlled in the red range. That is, by controlling the well width of the well layer having the quantum well structure, the emission wavelength of the semiconductor light emitting device can be controlled in the range from the ultraviolet region to the red region. FIG.
Taking a single quantum well layer composed of a well layer as an example, the well width (n
10 shows the result of calculating the relationship between m) and the emission energy.

The InN well layer has a layer thickness of 0.29 nm or more, and at least one of the GaN barrier layer and the InN well layer has an n-type or p-type carrier density of 1 × 10 ¹⁸ cm ⁻³ or more. It is preferred that As a result, the threshold current value of the semiconductor laser device is reduced, and the luminous efficiency of the light emitting diode can be increased.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the film forming method, the composition and thickness of the compound semiconductor layer, the process conditions, and the like described in the following embodiments and examples are merely examples for facilitating understanding of the present invention. However, the present invention is not limited to this example. Embodiment This embodiment is an example of an embodiment of a semiconductor light emitting device according to the present invention, and FIGS. 1A and 1B are main portions of the semiconductor light emitting device of the embodiment. FIG. 2 is a band diagram of a single quantum well structure and a multiple quantum well structure. The semiconductor light-emitting device of the present embodiment is, Al _x B _y Ga
_1-xyz In _z N (1> x ≧ 0, 1> y ≧ 0, and 1>
z> 0) -based semiconductor light emitting device having a single quantum well structure, in which GaN barrier layers 42A and 42B and GaN barrier layers 4
1 having an InN well layer 44 sandwiched between 2A and 2B.
An active layer having a single quantum well structure having a band structure as shown in FIG. In the example of the multiple quantum well structure, the semiconductor light emitting device of the present embodiment includes GaN barrier layers 46A to 46D and InN well layers 48A to 48C sandwiched between the barrier layers of the GaN barrier layers 46A to 46D, respectively. Having,
An active layer having a multiple quantum well structure having a band structure as shown in FIG. 1B is provided.

The semiconductor light emitting device of this embodiment is made of GaN.
By providing the barrier layer / InN well layer with a quantum well structure, the in-plane uniformity of the In composition of the active layer is improved, and the threshold current value is high, the differential gain is low, or the chip region of the semiconductor laser device, or The light emitting diode region having poor color purity is eliminated from the wafer, and the yield is improved. In other words, when applied to a semiconductor laser device, the threshold current value is low and the differential gain is increased on average, and when applied to a light emitting diode, the color purity is improved. Further, by controlling the thickness of the well layer of the quantum well structure of the semiconductor light emitting device, the emission wavelength can be accurately set in the range from the ultraviolet region to the red region.

Embodiment 1 In this embodiment, a semiconductor light emitting device according to the present invention is made of AlGaI.
FIG. 2 is a schematic diagram showing a layer structure of a semiconductor laser device of this embodiment, which is one of embodiments applied to an nN-based semiconductor laser device, and FIG. 2A is a schematic diagram of an active layer. . 2 that are the same as those shown in FIG. 4 are denoted by the same reference numerals. The same applies to FIG. The semiconductor laser device 60 of the present embodiment is an AlGaInN-based semiconductor laser device, and basically has the same configuration as the conventional AlGaInN-based semiconductor laser device 10 except for the configuration of the active layer 62. As shown in FIG. 2A, the active layer 62 has an InN well layer 62a having a well width of 0.87 nm.
And a GaN barrier layer 62b. InN
Since the well width of the well layer 62a is 0.87 nm, the emission wavelength becomes 472 nm.

The semiconductor laser device 60 is composed of a first GaN grown on a c-plane sapphire substrate 12 at a low temperature.
A buffer layer 14, a second buffer layer 16 made of GaN,
n-type GaN contact layer 18, first cladding layer 20 of n-type AlGaN, first light guide layer 22 of n-type GaN, active layer 62, second light guide layer 26 of p-type GaN, p-type AlGaN Second cladding layer 28,
And a p-type GaN contact layer 30 are sequentially laminated.

The n-type GaN contact layer 1 of the laminated structure
8, the first cladding layer 20, the first light guide layer 2
2. The active layer 62, the second light guide layer 26, the second cladding layer 28, and the p-type GaN contact layer 30 are formed as mesa portions extending in a predetermined direction. Further, as shown in FIG. 2, the semiconductor laser device 60 has an SCH structure, and the n-type first cladding layer 20 has a thickness of 1.0 μm and has a thickness of 1.0 μm.
The l-composition is 8%, and the p-type second cladding layer 28 has a thickness of 0.5 μm and an Al composition of 6%.

On the p-type contact layer 30, Ni
A p-side electrode 32 of a multilayer metal film such as an Au electrode is provided as an ohmic junction electrode, and an n-side electrode 34 of a multilayer metal film such as a Ti / Al electrode is It is provided as a bonding electrode.

Although the active layer 62 of the semiconductor laser device 60 of this embodiment has a single quantum well structure, it is not limited to this. For example, an active layer of a semiconductor laser device having a high power specification of several tens mW or the like has a well width of 0.87 nm.
It has a multiple quantum well structure composed of an N well layer and a GaN barrier layer having a layer width of 6 nm.

The laminated structure of the semiconductor laser device 60 of this embodiment is formed by epitaxial growth by MOCVD or MBE. In the case of the MOCVD method, the raw materials are TMG, TME, TMI, TMA, and NH ₃ , and SiH ₄ is used as an n-type dopant and bismethylcyclopentadienyl magnesium is used as a p-type dopant. In the case of the MBE method, the raw material is Al,
Ga, In, atomic N, Mg, and Si.

The conditions for growing the GaN barrier layer and the InN well layer are as follows. Growth method: MOCVD method Growth temperature: 500 ° C. Growth pressure: 760 Torr Source gas: Ga is TEG (triethyl gallium) In is TMI (trimethyl indium) N is NH ₃

Embodiment 2 The semiconductor laser device of this embodiment is the same as the semiconductor laser device except that the GaN barrier layer and the InN well layer of the quantum well are n-type with Si concentration of 1 × 10 ¹⁸ cm ^-3 due to Si doping. It has the same configuration as the semiconductor laser device 60 of the first embodiment. The effect of the doping is to cancel the built-in potential induced by the piezzo effect. The built-in potential causes a quantum Stark effect. By canceling the built-in potential, the threshold current value and the threshold voltage value can be reduced.

Embodiment 3 In this embodiment, a semiconductor light emitting device according to the present invention is formed of AlGaI.
FIG. 3 is a schematic diagram showing a layer structure of a light emitting diode of this embodiment, which is one of embodiments applied to an nN-based light emitting diode, and FIG. 3A is a schematic diagram of an active layer. The light-emitting diode 70 of this embodiment is an AlGaInN-based light-emitting diode, and a GaN buffer layer 74, a GaN buffer layer 76, an n-type GaN contact layer 78, and an n-type GaN buffer layer 74 grown at a low temperature on a c-plane sapphire substrate 72. AlGaN
It has a laminated structure in which a clad layer 80, an active layer 82, a p-type AlGaN clad layer 84, and a p-type GaN contact layer 86 are sequentially laminated.

In the laminated structure, the n-type GaN contact layer 7
8, n-type AlGaN cladding layer 80, active layer 8
2. The p-type AlGaN cladding layer 84 and the p-type GaN contact layer 86 are formed as mesa portions extending in a predetermined direction.

The active layer 82 is formed as shown in FIG.
It is composed of an InN well layer 82a having a well width of 0.87 nm and a GaN barrier layer 82b. Since the well width of the InN well layer 82a is 0.87 nm, the emission wavelength is 4
72 nm.

On the p-type contact layer 86, Ni
A p-side electrode 88 of a multilayer metal film such as an Au electrode is provided as an ohmic junction electrode, and an n-side electrode 90 of a multilayer metal film such as a Ti / Al electrode is provided on the n-type contact layer 78. It is provided as a bonding electrode.

The light emitting diode 80 of this embodiment is made of GaN
By providing the quantum well structure of the barrier layer and the InN well layer, the color purity is improved, and by controlling the thickness of the well layer, the emission wavelength can be accurately set in the range from the ultraviolet region to the red region. it can.

Embodiment 4 The light emitting diode of this embodiment is identical to the light emitting diode except that the GaN barrier layer and the InN well layer of the quantum well are n-type with Si concentration of 1 × 10 ¹⁸ cm ⁻³ by Si doping. Example 3
The same configuration as that of the light emitting diode 80 is provided. The effect of doping is to increase the luminous efficiency by canceling the built-in potential induced by the piezo effect.
The built-in potential causes a quantum Stark effect.

[0033]

According to the present invention, a group III compound other than In can be used.
A barrier layer made of an original group III nitride compound semiconductor;
AlBGaIn as a quantum well structure with a well layer composed of
When the present invention is applied to a semiconductor laser device by forming an active layer of an N-based semiconductor light-emitting device, an AlBGaInN-based semiconductor laser device having a low threshold current value and a large differential gain can be realized. Further, when applied to a light emitting diode, color purity can be increased. In addition, well layers and / or
Alternatively, by doping the barrier layer, AlB
The threshold current value of the GaInN-based semiconductor laser device can be reduced, and the luminous efficiency of the AlBGaInN-based light-emitting diode can be increased. Further, by adjusting the thickness of the well layer, the emission wavelength of the semiconductor light emitting device can be accurately controlled in the range from ultraviolet to red.

[Brief description of the drawings]

FIGS. 1A and 1B are a band diagram of a single quantum well structure and a band diagram of a multiple quantum well structure, respectively, which are main parts of a semiconductor light emitting device according to an embodiment.

FIG. 2 is a schematic diagram showing a layer structure of the semiconductor laser device of Example 1, and FIG. 2A is a schematic diagram of an active layer.

FIG. 3 is a schematic diagram illustrating a layer structure of a light emitting diode of Example 3, and FIG. 3A is a schematic diagram of an active layer.

FIG. 4 is a schematic diagram showing a layer structure of a conventional semiconductor laser device.

FIG. 5 is a graph showing a relationship between a well width of a well layer and photon energy.

[Explanation of symbols]

10: Conventional AlGaInN based semiconductor laser device, 1
2 ... Sapphire substrate, 14 ... Ga grown at low temperature
N. a first buffer layer made of N, 16... A second buffer layer made of GaN, 18.
... First cladding layer made of n-type AlGaN, 22
First optical guide layer made of n-type GaN, 24... Ga _1-x
In _x N / Ga _1-y In _y N multiple quantum well structure active layer 26... Second optical guide layer made of p-type GaN 28
... Second cladding layer made of p-type AlGaN, 30
p-type GaN contact layer, 32... p-side electrode, 34.
n-side electrode, 42A, B ... GaN barrier layer, 44 ... In
N well layers, 46A to D ... barrier layers, 48A to C ... well layers, 60 ... AlGaInN based semiconductor laser device of Example 1, 62 active layers (consisting of InN well layers 62a and GaN barrier layers 62b) Quantum well structure), 70
... AlGaInN-based light emitting diode of Example 3, 72
…… Sapphire substrate, 74 …… GaN grown at low temperature
Buffer layer, 76 GaN buffer layer, 78 n-type GaN contact layer, 80 n-type AlGaN cladding layer, 82 active layer (including InN well layer 82a and GaN barrier layer 82b Quantum well structure), 84
... p-type AlGaN cladding layer, 86 ... p-type GaN contact layer, 88 ... p-side electrode, 90 ... ... n-side electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA11 AA41 CA03 CA05 CA34 CA57 CB05 5F045 AA04 AB14 AB19 AC08 AC09 AC12 AD09 AF09 CA10 CA12 DA55 DA60 5F073 AA11 AA73 AA74 CB05 CB13 CB22 DA05 EA07 EA23

Claims (5)

[Claims] Al _x B _y Ga _1-xyz with claim 1 active layer
In _z N (1> x ≧ 0, 1> y ≧ 0, and 1>z> 0)
In the semiconductor light emitting device, the active layer is formed as a quantum well structure including a barrier layer made of a group III binary group III nitride compound semiconductor other than In and a well layer made of InN. Semiconductor light emitting device. 2. The semiconductor light emitting device according to claim 1, wherein the barrier layer is a GaN layer. 3. The semiconductor light emitting device according to claim 2, wherein the InN well layer has a layer thickness of 0.29 nm or more. 4. The device according to claim 2, wherein at least one of the GaN barrier layer and the InN well layer has an n-type or p-type carrier density of 1 × 10 ¹⁸ cm ⁻³ or more. Semiconductor light emitting device. 5. The semiconductor light emitting device according to claim 4, wherein the n-type carrier density is adjusted by a Si dopant.