JP2001085739A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To emit light of high efficiency in an ultraviolet region by providing an AlGaN semiconductor layer where boron elements are doped for a semiconductor device. SOLUTION: An AlGaN layer 2, an AlGaN layer 3 where boron elements are doped and a p-type AlGaN layer 4 are sequentially laminated on a sapphire substrate 1 and they are grown. The p-type AlGaN layer 4 and the AlGaN layer 3 are partly selectively removed by dry etching and the desired area of the n-type AlGaN layer 2 is exposed. Then, an n-type electrode 5 formed of a Ti/Al film and a p-type electrode 6 formed of Ni/Au film are formed by using electron beam vapor-deposition and photoetching. Thus, light emission efficiency in an ultraviolet region can considerably be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device,
More specifically, the present invention relates to a semiconductor device using a group III nitride semiconductor and having high luminous efficiency in an ultraviolet region.

[0002]

2. Description of the Related Art Light emitting diodes and semiconductor lasers that emit light in the ultraviolet region are expected to be widely applied to light sources for high-density recording media and are being actively studied. The active layer of the optical device for these ultraviolet region, but A1 _1-x Ga _x N layer having a band gap greater than 3.4eV of GaN is known, the emission of a deep level caused by crystal defects This is problematic in that light emission near the band gap is weak.

[0003] At present, an InGaN layer is generally used as an active layer, and a semiconductor laser that continuously oscillates at a wavelength of about 400 nm at room temperature has been realized.

[0004]

However, in recent years, there has been a strong demand for an optical device that emits light at a shorter wavelength. In order to realize an optical device suitable for operation at such short wavelength zone, A1 _1-x Ga _x N layer but it is necessary to use as the active layer, conventional A1 _1-x Ga _x N the layer, there are problems as described above, is sufficiently high luminous efficiency at a band edge, it is difficult to grow a high-quality A1 _1-x Ga _x N layer. Therefore, optical devices for short-wavelength emission efficiency is high with A1 _1-x Ga _x N layer as the active layer is not currently implemented.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an A light source capable of emitting light with high efficiency in the ultraviolet region.
An object of the present invention is to provide a semiconductor device using an _11-x Ga _x N layer as an active layer.

[0006]

To achieve the above object, according to an aspect of the semiconductor device of the present invention is characterized by having a boron (B) Al element is doped _1-x Ga _x N semiconductor layer.

That is, in the present invention, A11 _-xG
by doping a _x N layer of boron (B) element, is level is formed called isoelectronic trap is improved luminous efficiency in the ultraviolet region, a high efficient light emission capable optical device in the ultraviolet region Is realized.

It is known that an isoelectronic trap in a semiconductor is formed when GaP is doped with nitrogen. In this case, N in GaP
Is substituted with P, but neither of them is a group V atom, so they cannot be a donor or an acceptor. However, since N has a higher electronegativity than P, it acts as an isoelectronic trap, and electrons are captured by neutral N. Further, holes are trapped by the Coulomb force of the electrons trapped by N, and excitons trapped at the center of neutral N are formed. The recombination light emission of this exciton is used for light emission of the device.

In the present invention, when A1 _1-x Ga _x N is doped with boron (B), the doped B becomes Ga
Or, it is substituted with A1. Since B has a higher electronegativity than Ga and A1, neutral B forms an isoelectronic trap to capture electrons. As a result, excitons are formed by electrons trapped at the center of neutral B, and the element emits light.

J. C. According to the semiconductor coupling theory of Phi11ips (Academic Press Japanese version, Takeichi Komatsubara, translation, 1976.8.25, Yoshioka Shoten), the electronegativity is 2 for B, 1.13 for Ga and 1.18 for A1. Since B has much higher electronegativity than Ga and Al, B also has a large effect as an isoelectronic trap for capturing electrons.

[0011] The semiconductor device of the present invention, since the boron (B) has a A1 _1-x Ga _x N layer doped by the isoelectronic trap improves the luminous efficiency in the ultraviolet region, a high An efficient optical device is realized. In addition, since the emission of deep levels due to crystal defects is extremely small, it is not necessary to increase the growth temperature.

The present invention can be carried out in various modes. One of the most typical modes is one of the surfaces of the Al _{1 -x} Ga _x N semiconductor layer doped with boron (B). n-type A1 _1-y Ga _y n a (y <x) layer is disposed on the, by placing a p-type _{A1 1-y Ga y n (} y <x) layer on the other surface, a semiconductor element This is an example of the configuration. N-type A on the side of the substrate
_{1 1-y} Ga _y N Place (y <x) layer, the substrate may be disposed a p-type _{A1 1-y Ga y N (} y <x) layer on the side opposite but, n-type A1 _{1-y Ga y N (y} <x) layer and a p-type A1 _1-y G
It goes without saying that the arrangement of the a _y N (y <x) layers may be reversed.

In the present invention, a very preferable result can be obtained if the boron (B) doping concentration of the Al _{1 -x} Ga _x N semiconductor layer is 1 × 10 ¹⁷ cm ^-3 or more. Even if the boron (B) doping concentration becomes high, no obstacle is particularly generated, and therefore, it may be raised to the solid solution limit.

The above-mentioned Al doped with boron (B)
Of _1-x Ga x N semiconductor layer, the n-type _{A1 1-y Ga y N (} y <x) layer disposed on the one side, has a 1 × 10 ¹⁷ cm ^-3 or more electron concentration it is preferable that, p-type disposed on the other surface _{A1 1-y Ga y N (} y <x) layer, 1 ×
It preferably has a hole concentration of 10 ¹⁷ cm ^-3 or more. In the double hetero structure, it is preferable that y <x in order to confine electrons and holes in the active layer. The p-type electrode and the n-type electrode can be appropriately selected from various known electrodes.

[0015]

Embodiment 1 FIG. 1 shows a sectional structure of an embodiment of the present invention. In Figure 1, reference numeral 1 is a sapphire substrate, 2 n-type A1 _1-Tsu Ga _y N with 1 × 10 ¹⁷ cm ^-3 or more electron concentration that is grown on a sapphire substrate 1 (y <x) layer (film thickness 2 [mu] m), is the n-type A1 _1-y Ga y layer 2 B doped grown on A1 _1-x Ga x n layer (thickness 0.1 [mu] m 3), is 4 the B-doped A1 _1-x Ga 1 × 10 ¹⁷ c grown on _xN layer 3
p-type having m ^-3 or more hole concentration _{A1 1-y Ga y N (} y <
x) layers (film thickness 0.5 μm) are each represented. The growth of each layer is performed by using a well-known atmospheric pressure MOVPF apparatus, and trimethylgallium and trimethylaluminum are used as a group III element material, ammonia is used as a group V element material,
Diborane is used as a doping material for B,
The growth was performed at a growth temperature of 1100 ° C. By doping B with diborane, B can be doped with good controllability from a B doping concentration of 10 ¹⁷ cm ^-3 or more to several%. In addition, silane was used as the n-type doping material, and bis-cyclopentadienyl magnesium was used as the p-type doping material.

[0016] After the growth by sequentially laminating the n-type A1 _1-Tsu Ga _y N layer 2, B-doped A1 _1-x Ga x N layer 3 and p-type A1 _1-y Ga y N layer 4, the well-known p-type dry etching A1 _1-y Ga y N layer 4 and the B-doped A1 _1-x G
A portion of the a _x N layer 3 is selectively removed to form an n-type A1 _1-y Ga
_y After exposing a desired region of the N layer 2, an n-type electrode 5 made of a Ti / Al film having a thickness of 2000 ° and a thickness of 2000 are formed by using well-known electron beam evaporation and photoetching.
The p-type electrode 6 made of the Ni / Au film of Å was formed.

FIG. 2 shows an emission spectrum at the time of current injection when the B-doped A1 _1-x Ga _x N layer 3 of x = 0.9 is used as an active layer in the structure shown in FIG. . For comparison, in the structure shown in FIG. 1, B is a A1 _1-x Ga _x layer of x = 0.9 that is not doped, the emission spectrum at the time of current injection in the case of using as an active layer in FIG. 2 Indicated. Note that the light emission intensity shown on the vertical axis in FIG.

[0018] As apparent from FIG. 2, in the case where B is with A1 _1-x Ga x layer of x = 0.9 that is not doped as the active layer, Al in the vicinity of a wavelength of 330nm
Weak band edge emission of the _0.1 Ga _0.9 N layer was observed, and emission from a deep level near 500 to 550 nm was observed.

A1 _1-x Ga _x not doped with B
Light emission from a deep level observed in the case of using a layer as the active layer is thought to be due to a defect having a A1 _1-x Ga _x layer, in order to reduce such defects, The semiconductor layer must be grown at a substrate temperature higher than 1100 ° C.

On the other hand, B-doped A11 _-x Ga _x
In the case of the structure of FIG. 1 in which the layer 3 is used as the active
On the low energy side of several tens of mW from the emission near the band edge near 30 nm, sharp emission with a small wavelength width and extremely high emission intensity was observed. This sharp light emission is considered to be due to light emission involving an isoelectronic trap due to doped B. Thus, by using B is to A1 _1-x Ga _x layer doped as the active layer, luminous efficiency is greatly improved, it became possible to realize a high-efficiency ultraviolet region light device.

Further, A1 in which B is not doped
The _1-x Ga _x layer was observed when used as the active layer, light emission in the vicinity of the 500~550nm was not observed, A1
Light emission from a deep level caused by defects included in the _1-x Ga _x layer, it does not occur is confirmed.

In this embodiment, the case where x = 0.9 has been described. However, the present invention is not limited to the case where x = 0.9.
Is more than 0 and less than 1, preferable results can be obtained.

[0023]

Effect of the Invention] As described above in detail, according to the present invention, by doping B to A1 _1-x Ga _x N layer is an active layer, to form a level called isoelectronic trap As a result, the luminous efficiency in the ultraviolet region was significantly improved. Furthermore, since light emission from deep levels caused by crystal defects is effectively prevented, an optical device having extremely high luminous efficiency in the ultraviolet region can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram comparing emission spectra of the present invention and a conventional example.

[Explanation of symbols]

1 ... sapphire substrate, 2 ... n-type Al _1-y Ga y N layer, 3 ...
B doping Al _1-x Ga x N layer, 4 ... p-type Al _1-y Ga y
N layer, 5 ... n-type metal electrode, 6 ... p-type metal electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA03 CA03 CA34 CA46 CA57 CA65 CA74 CA82 CA92 5F073 CA07 CB05 CB17 CB22 DA05 DA21 EA07

Claims (3)

[Claims] 1. A doped with boron (B) element
A semiconductor device having an l _1-x Ga _x N semiconductor layer. According to claim 2 wherein the Al _1-x Ga _x N semiconductor layers are n-type _{A1 1-y Ga y N (} y <x) layer on top of one side formed, on the other surface p-type _{A1 1-y Ga y N (} y <x) the semiconductor device according to claim 1, characterized in that layer is formed. 3. The semiconductor device according to claim 1, wherein a doping concentration of the boron (B) element is 1 × 10 ¹⁷ cm ⁻³ or more.