JP2890392B2 - III-V nitride semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group III-V nitride semiconductor (In _x Al _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦ Y, X + Y ≦ 1).
A light-emitting element comprising:

[0002]

2. Description of the Related Art InN of a III-V nitride semiconductor is 1.9.
5 eV, GaN has a band gap energy of 3.4 eV, and AlN has a band gap energy of 6.0 eV. The mixed crystal of these nitrides, In _x Al _Y Ga ₁ -XYN, has a band gap of 1.95 to 6 depending on the composition ratio. 0.0eV, so that light emitting diodes (LEDs) in the ultraviolet and visible regions
Attention has been paid to materials for light-emitting elements such as laser diodes (LDs). Recently, the world's first blue LED has been realized using this material.

FIG. 1 shows the structure of a light emitting element used in a current blue LED. Basically, on a substrate 11 made of sapphire, an n-type contact layer 12 made of Si-doped n-type GaN, an n-type clad layer 13 made of Si-doped n-type GaAlN layer, Zn, Si-doped InGa
It has a double hetero structure in which an active layer 14 of N, a p-cladding layer 15 of Mg-doped p-type GaAlN layer, and a p-contact layer 16 of Mg-doped GaN are sequentially stacked. Usually, the substrate 11 and the n-contact layer 1
2, a buffer layer of GaN, AlN or the like is formed, but is not particularly shown. This light emitting device emits 450 n by light emission of Zn and Si doped InGaN which is the active layer 14.
Blue to blue-green emission of m to 520 nm. FIG. 2 shows an example of the emission spectrum.

The spectrum shown in FIG. 2 shows a blue LED having a main light emission peak near 450 nm. The main light emission peak near 450 nm is a peak due to an impurity level.
The peak near 90 nm is a peak due to InGaN interband emission.

[0005]

However, the conventional light-emitting device has a problem that the half-width of the emission spectrum is widened and the emission looks whitish because the main emission peak is obtained by impurities. Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to increase the color purity by reducing the half-value width of the emission spectrum of a light-emitting element comprising a III-V nitride semiconductor. .

[0006]

SUMMARY OF THE INVENTION A group III-V nitride semiconductor light-emitting device according to the present invention comprises a group III-V nitride semiconductor (In _X Al _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦ Y, X + Y
≦ 1) in a group III-V nitride semiconductor light emitting device having a light emitting layer stacked thereon, wherein the light emitting layer contains indium.
Consisting of an IV nitride semiconductor and further constituting a light emitting layer
At least one layer having a band gap smaller than that of the group III-V nitride semiconductor is formed in a layer other than the light-emitting layer.

In a preferred embodiment of the light emitting device according to the present invention, the light emitting layer has a first main surface and a second main surface, and is formed of an active layer made of a group III-V nitride semiconductor containing indium. A main surface of the active layer has a double hetero structure sandwiched between a first cladding layer and a second cladding layer, and has a smaller band gap than the III-V compound semiconductor of the light emitting layer. A light-emitting element in which a layer made of a III-V compound semiconductor is formed outside the first cladding layer and / or the second cladding layer.

In a further preferred embodiment, when an electrode is formed in a layer having a smaller band gap than the light emitting layer, ohmic contact between the electrode material and the III-V nitride semiconductor layer having a smaller band gap is easily made, so that the efficiency of the light emitting device is improved. It is very preferable in improving the quality.

[0009]

Generally, in a group III-V nitride semiconductor having a double hetero structure, an active layer is sandwiched between cladding layers having a band gap energy larger than that of the active layer. In the present invention, by forming a layer having a band gap energy smaller than the active layer outside the cladding layer,
A layer having a smaller band gap absorbs a part of light emitted from a band gap layer having a larger band gap. That is, in the spectrum of FIG.
When a group III-V compound semiconductor layer having a band gap smaller than that of (e.g., InGaN having an In composition ratio matching 440 nm) is formed outside the cladding layer, light having a wavelength shorter than 440 nm is emitted. It is absorbed by the small band gap layer. As a result, the half width of the spectrum is narrowed, and the color purity of the emitted light can be improved. However, it is needless to say that the composition ratio of the layer having a small band gap is adjusted so as not to absorb the main emission wavelength of the light emitting element.

This effect is not limited to a light emitting device having a double hetero structure, but is also applicable to a device having a single hetero structure or a homo structure. For example, in a light emitting device having a homo structure having a main emission peak at 430 nm using a Mg-doped p-type GaN layer as a light emitting layer, a layer having a smaller band gap than GaN (3.4 eV) (for example, a 420 nm band gap) Forming an InGaN layer corresponding to
Light having a wavelength shorter than 420 nm is absorbed by the InGaN layer.

[0011]

【Example】

Embodiment 1 FIG. 3 shows the structure of a light emitting device according to one embodiment of the present invention. This is because a layer 88 having a smaller band gap than the light emitting layer (hereinafter, referred to as a small band gap layer), an n-type contact layer 2, and a first cladding layer 3 are formed on the substrate 1.
, An active layer 4, a second cladding layer 5, a p-type contact layer 6, and another small band gap layer 88 'are sequentially stacked.

Sapphire (A-plane, C-plane, R
Including planes. ), SiC, ZnO, Si and the like can be used.

[0013] n-type contact layer 2 is _{Si, Ge, In X Al Y} Ga 1-XY N (0 ≦ containing n-type dopant such as Sn
X, 0 ≦ Y, X + Y ≦ 1), and in order to obtain a contact layer with good crystallinity, it is preferable to use GaN or GaAs.
to form 1N.

The n-type cladding layer 3 is a first cladding layer, and also includes In _x Al _Y Ga _{1 -XYN} (0 ≦ X, 0 ≦ Y, X + Y ≦) containing an n-type dopant such as Si, Ge, Sn or the like. It can be formed in 1). In order to obtain a cladding layer having good crystallinity, GaN and GaAlN are preferably formed. However,
If only a double hetero structure is to be realized, either the n-type contact layer 2 or the n-type cladding layer 3 may be omitted. If omitted, the remaining n-type layer functions as a cladding layer and a contact layer.

The active layer 4 is a light emitting layer and is preferably made of a III-V nitride semiconductor containing indium. More preferably, the n-type dopant and / or Zn, M
In _X Al _Y Ga _{1 -XYN} (0 <X, 0 ≦ Y, X + Y ≦
Formed in 1). The active layer containing indium can freely change the emission color from ultraviolet to orange depending on the indium content ratio, and is very preferable in realizing a light emitting device in the visible region, and in order to obtain an active layer with good crystallinity, Preferably, InGaN is formed. However, in the case of the double hetero structure, as described above, In _x Al _Y Ga _{1-XY is used} so that the band gap of the active layer is smaller than that of the cladding layer.
It goes without saying that the composition ratio of N is adjusted.

The p-type cladding layer 5 is a second cladding layer, which is also made of In _x containing a p-type dopant such as Zn or Mg.
In order to obtain a cladding layer that can be formed of Al _Y Ga _{1 -XYN} (0 ≦ X, 0 ≦ Y, X + Y ≦ 1), has good crystallinity, and exhibits favorable p-type characteristics, it is necessary to use Mg-doped GaN. Or GaAlN is formed.

The p-type contact layer 6 is also made of In _x Al _Y Ga _{1 -XYN} (0 ≦ X, 0 ≦ Y, X + Y) containing a p-type dopant.
≦ 1), similarly, to obtain a cladding layer having good crystallinity and exhibiting preferable p-type characteristics, GaN or GaAlN preferably doped with Mg is formed. However, if only a double hetero structure is realized, any of the p-type cladding layer 5 and the p-type contact layer 6 may be omitted. If omitted, the remaining p-type layer functions as a cladding layer and a contact layer.

[0018] Next is a small band gap layer 88, 88 ', which is a feature of the present invention and these form a small _{In X Al Y Ga 1-XY} N layer band gap than the active layer 4. For example, when the active layer is In0.1Ga0.9N, the band gap can be made smaller than that of the active layer.
This can be realized by forming N.

In particular, in a blue light-emitting device using a III-V group nitride semiconductor containing In as an active layer, as shown in FIG. 2, a peak showing inter-band emission of InGaN often appears on the short wavelength side of the spectrum. The peak intensity of the interband emission tends to increase when the current value of the light emitting element is increased. When the inter-band light emission becomes strong, the luminous efficiency of the light-emitting element decreases, and the luminescent color tends to shift. Therefore, it is very convenient to eliminate the inter-band light emission. Therefore, when a small bandgap layer is formed as in the present invention, light emission between bands is absorbed, so that a light-emitting element which shows a preferable light emission color without a shift in light emission color can be realized.

In FIG. 3, the small band gap layer 88,
Although 88 'is formed on both sides of the first cladding layer and the second cladding layer, it goes without saying that it may be formed on either one of them. When it is formed on either one, it is desirable to form it on the outside of the cladding layer on the emission observation surface side. Further, when the p-contact layer 6 is omitted and the small band gap layer 88 ′ is doped with a p-type dopant such as Mg or Zn to be p-type and the p-contact layer on which an electrode is to be formed, ohmic contact with the electrode is obtained. And the luminous efficiency is improved.

Embodiment 2 FIG. 4 is also a cross-sectional view showing one structure of the light emitting device of the present invention. This is because a Si-doped n + -type GaN layer 22 having a high electron carrier concentration is
Si-doped n-type GaN23 with low electron carrier concentration
And a light emitting device in which Mg-doped p-type GaN 24 and InGaN 99 having a band gap smaller than GaN, for example, having a band gap of 400 nm, are shown.

In this light emitting device, the light emitting layer is made of Mg-doped GaN.
The layer 24 has an emission peak near 430 nm. However, since the small bandgap layer 99 is provided, the small bandgap layer 99 absorbs a wavelength of 400 nm or less. Therefore, since the light emitting element in which the ultraviolet portion is cut is realized, it is possible to realize a light emitting element that does not adversely affect the mold resin.

[0023]

As described above, according to the present invention,
When a layer having a smaller band gap than the light emitting layer is formed,
The layer absorbs wavelengths having energy greater than its bandgap energy. Generally, a light emitting device such as an LED is formed by molding a light emitting element with a resin such as an epoxy resin. Therefore, when a blue light emitting element is realized by using a III-V nitride semiconductor, according to the present invention, a preferable light emitting device in which a mold resin is hardly deteriorated can be realized because an ultraviolet portion is cut.

Further, when a green light-emitting element is realized by an active layer containing indium, according to the present invention, a blue light portion can be cut, so that color purity is improved and a preferable light-emitting element can be provided.

Further, since the filter is formed of the same material as the semiconductor constituting the light emitting element, a light emitting element which is preferable in terms of production technology and excellent in reliability can be provided, and its industrial utility value is enormous.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one structure of a conventional III-V nitride semiconductor light emitting device.

FIG. 2 is a diagram showing an emission spectrum of a conventional III-V nitride semiconductor light emitting device.

FIG. 3 is a schematic sectional view showing the structure of a group III-V nitride semiconductor light emitting device according to one embodiment of the present invention.

FIG. 4 is a schematic sectional view showing the structure of a group III-V nitride semiconductor light emitting device according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... n contact layer 3 ... n clad layer 4 ... active layer 5 ... p clad layer 6 ... p contact layer 88, 88 '... small band gap layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 33/00 H01S 3/18 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A group III-V nitride semiconductor having different conductivity types (In _X Al _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦ Y, X + Y ≦
1) A group III-V nitride semiconductor light-emitting device comprising a light-emitting layer laminated thereon, wherein the light-emitting layer is made of a group III-V nitride semiconductor containing indium, and a group III-V nitride constituting a light-emitting layer A layer having a band gap smaller than that of a semiconductor is formed in at least one layer in a layer other than the light-emitting layer. II
Group IV nitride semiconductor light emitting device. 2. The light-emitting element according to claim 1, wherein the light-emitting layer has a double hetero structure in which a light-emitting layer is sandwiched between a first clad layer and a second clad layer. 2. The layer according to claim 1, wherein a layer made of a III-V compound semiconductor having a smaller band gap is formed outside the first cladding layer and / or the second cladding layer. 3. III-V nitride semiconductor light emitting device. 3. An electrode is formed in a layer having a smaller band gap than the light emitting layer.
Or the group III-V nitride semiconductor light emitting device according to claim 2.