JP2791448B2 - Light emitting diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride-based compound
Relates to a light emitting diode made of a conductor, particularly high emission efficiency, high brightness, and good color purity, the present invention relates to a light emitting diode.

[0002]

2. Description of the Related Art At present, a blue light emitting diode using a gallium nitride compound semiconductor has a well-known MIS structure shown in FIG.

In general, a blue light emitting diode having an MIS structure basically includes a sapphire substrate 1, a buffer layer 2 made of AlN, a Si-doped n-type Ga _x Al _{1 -x} N layer 3,
n-doped i-type Ga _X Al _1-X N layer 4 are laminated in this order, the electrodes 3 and 4 has a retrieved structure. The blue light-emitting diode having such a MIS structure gallium nitride-based compound semiconductor has a higher luminous efficiency than other semiconductor materials having a pn junction, for example, a red light-emitting diode made of GaAlAs, GaP, or the like, or a green light-emitting diode. Because of the low brightness and low brightness, it was still insufficient for practical use.

[0004]

The reason why only the blue light emitting diode having the MIS structure can be put to practical use is as follows.
To obtain a light emitting active layer, Z as a p-type dopant
This is because even if n is doped into a gallium nitride-based compound semiconductor, the semiconductor does not become p-type and becomes only high-resistance i-type.
Note that the high-resistance i-type here means a resistivity of 10 ⁸ Ω · cm or more.

There is also an attempt to obtain a p-type layer by doping Mg instead of Zn as a p-type dopant, and a low-resistance p-type layer can be obtained by doping Mg. However, since the emission wavelength of the p-type layer is violet having a wavelength shorter than that of blue, it is impossible to obtain a blue light-emitting diode having good color purity by using a pn junction having a structure in which Mg is the emission center. .

As described above, it is very difficult to obtain a pn junction blue light-emitting diode using a gallium nitride-based compound semiconductor, so that only a MIS structure blue light-emitting diode is currently available. Is the actual situation.

As is well known, in consideration of light emission characteristics represented by light emission output, reliability, and the like, the pn structure is more pn-type than the MIS structure.
It is common sense that joining is advantageous, as soon as possible, pn
The realization of a junction blue light emitting diode is strongly desired.

Accordingly, the present invention has been made in view of the above circumstances, and realizes a light emitting diode having a structure in which a light emitting active layer is sandwiched between a p-type layer and an n-type layer, thereby achieving high efficiency and high luminance. An object of the present invention is to provide a light emitting diode having excellent light emitting characteristics such as color purity.

[0009]

SUMMARY OF THE INVENTION The present invention provides gallium nitride.
Diodes with Double Heterostructures Made of Palladium-Based Compound Semiconductors
Ga _X Al _{1 -X} N (where X is in the range of 0 <X ≦ 1).
In the box. ) And a Si-doped buffer layer
N-type cladding layer and Zn-doped light emitting
Layer and Mg-doped p-type cladding layer
And characterized in that:

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a light emitting diode according to one embodiment of the present invention.
The structure is shown in FIG. The light emitting diode of the present invention shown in FIG. 1 has a structure in which Ga _X Al ₁ -XN (0 <X ≦
1) buffer layer 12 composed of 1) Si-doped n-type Ga _x Al _{1 -x} N layer 3 which is an n-type clad layer doped with Si
(Hereinafter referred to as an n-type cladding layer), a Zn-doped Ga _x Al ₁ -xN layer 14 which is a light emitting active layer doped with Zn.
(Hereinafter, referred to as an active layer), and a Mg-doped p-type Ga _x Al _1-x N layer 5 (hereinafter, referred to as a p-type cladding layer) which is a p-type cladding layer doped with Mg.
Electrodes are taken out of 3 and 5.

The buffer layer 12 is necessary to improve the crystallinity of the gallium nitride-based compound semiconductor layer laminated thereon, and is usually formed to a thickness of several nm to several hundred nm or less. The buffer layer 12 may be formed on the n-type cladding layer 3 and the active layer 14 in addition to the sapphire substrate.

The active layer 14 has Zn as an emission center, and has a peak emission wavelength at about 470 to 480 nm.

In the light-emitting diode of the present invention, the function of the buffer layer 12 is described in Japanese Patent Application No. Hei.
No. 32259 describes this in detail. Simply put, the material of the buffer layer is more Ga than the conventional AlN.
_When XAl ₁ -XN (0 <X ≦ 1) is satisfied, the crystallinity of the gallium nitride-based compound semiconductor grown thereon is remarkably improved, and Mg-doped Ga _X Al _1- grown on the gallium nitride-based compound semiconductor is further improved. _This means that the XN layer easily becomes p-type.

The material of the buffer layer 12 is Ga _x Al _{1 -x}
By setting N (0 <X ≦ 1), also in the active layer 14, the conventional i-type Ga _x Al
_{Since the} crystallinity is remarkably improved as compared with the _1-X N layer 4, the resistivity becomes 10 ⁵ Ω · cm or less.

Therefore, when the light emitting diode has the above structure , the p- type cladding layer 5 easily becomes p-type.
When a current is caused to flow by setting the p- type cladding layer 5 to the + (plus) side and the n-type cladding layer 3 to the-(minus) side, p
Holes are injected into the active layer 4 from the mold cladding layer 5 and electrons are injected from the n-type cladding layer 3 at the same time. The holes and electrons are recombined in the active layer 4 which is the light emitting layer, and the color is emitted with Zn as the emission center. It emits blue light with good purity.

As described above, without the buffer layer 12, a p-type layer cannot be obtained, and it is impossible to obtain a light emitting diode having the structure of the present invention.

[0017]

As described above, the light-emitting diode of the present invention sandwiches an active layer that emits light between p-type and n-type gallium nitride-based compound semiconductor layers and activates electrons and holes. The light emission mechanism is the same as that of a light emitting diode having a double hetero structure, for example, by injecting the light into the layer.
Compared to the light emitting diodes of the S structure, high efficiency, and high brightness, it is possible to realize a color purity with good light-emitting diodes. Moreover, in the present invention, Ga _X Al _{1 -X} N (0 <X ≦
1) and an n-type silicon doped with Si.
Lad layer, active layer doped with Zn, and doped with Mg
Combination with the p-type cladding layer
A light emitting diode made of a nitride semiconductor can be realized.

Further, since the light emitting diode of the present invention has Ga _x Al _{1 -x} N (0 <x ≦ 1) in the buffer layer,
The crystallinity of the compound semiconductor laminated on the sapphire substrate is significantly improved. Therefore, the p-type clad layer laminated on the AlN buffer layer and the Ga _x
The crystallinity of the p-type cladding layer formed on the Al _1-x N (0 <x ≦ 1) buffer layer is significantly different. Therefore, the light emitting diode of the present invention having excellent crystallinity naturally has high luminance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a light emitting diode of the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a conventional light emitting diode.

[Explanation of symbols]

1 ... sapphire substrate 2 ... AlN buffer layer 3 ... n-type cladding layer 4 ... i-type Ga _X Al _1-X N layer 5 ... p-type cladding layer 12 ... Ga _X Al _1-X N (0 <X ≦ 1) buffer layer 14 ... active layer

Claims (1)

(57) [Claims] 1. A semiconductor comprising a gallium nitride-based compound semiconductor.
A light emitting diode having a bull hetero structure, wherein Ga _X Al
_A buffer layer made of _1-X N (where X is in the range of 0 <X ≦ 1); an n-type clad layer doped with Si;
A light-emitting diode comprising: a light-emitting active layer doped with Zn; and a p-type clad layer doped with Mg .