JPS6342192A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To prevent low threshold value and deterioration in temperature characteristic, by constituting an active layer and a clad layer of a III-V semiconductor which includes part of or all of alumina, gallium and indium as group III elements and includes phosphorus as a group V element, and using a double heterostructure in which arsenic is added and included in the active layer. CONSTITUTION:On an n-type GaAs substrate 1, the following layers are sequentially grown by an MO-VPE method and the like: an n-type Al0.5In0.5P clad layer 2 having a thickness of 1mum; a non-doped (Al0.45Ga0.55)0.6In0.4P0.8As0.2 active layer 3 having a thickness of 0.1 mum; a p-type Al0.5In0.5P clad layer 4 having a thickness of 1mum; and an n-type GaAs current blocking layer 5 having a thickness of 0.5mum. Then, only a part of n-GaAs blocking layer 5, which corresponds to a stripe part 9 having a width of about 2-10mum, is selectively etched away by a photolithography method and the like. Then a p-GaAs cap layer 6 is grown by about 1mum. A p-type electrode 7 composed of Ti/Pt/Au is formed on the layer 6. An n-type electrode 8 composed of Au/Ge is formed on the rear surface of the n-GaAs substrate 1.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a high performance visible light semiconductor light emitting device.

(Prior art) A III + V group semiconductor (hereinafter referred to as AeGaInP) containing some or all of aluminum, gallium, and indium as a group III element and phosphorus as a group
A double-hetero structure in which a layer (referred to as a "based semiconductor") is used as an active layer and a cladding layer is used as a semiconductor light-emitting element that oscillates or emits light in the visible light region of about 580 nm to 690 nm in wavelength. Conventional structure of a semiconductor laser made of AeGaInP system (Electronics Luthers)
A schematic perspective view of the Electron, Lett, X1985) is shown in FIG. n-(Ae□, 5Gao, s)o, 5Ino, with a thickness of lpm on the n-GaAs substrate 51.
5P clad R52, 0.1 pm thick undoped (
Aro, IGao, 9)o, 5Ino, 5P active layer 53
, p-(Ae□,5 Ga□,5)0.5 with thickness lpm
An n-GaAs current blocking layer 55 made of In□, 5P54, and 0.5 pm thick is sequentially grown epitaxially.

Next, by photolithography or the like, only the striped portion 59 with a width of about 10 pm is formed on the n-GaAs block layer 55.
selectively etched and removed. Then p-GaA
s cap layer 56 is grown to a thickness of about 1 pm, and Ti/
P-electrode 57 made of Pt/Au, n-GaAs substrate 51
An n-electrode 58 made of Au/Ge is formed on the back surface of the substrate. This laser oscillates in red at 660 nm.

(Problems to be Solved by the Invention) When a double heterostructure is constructed, the height of the energy step formed at the heterojunction (where the height of the energy step in the conduction band is ΔEc and that in the valence band is ΔEv) is as follows:
It is determined by the energy gap difference (ΔEg) and the distribution ratio to each layer. When a semiconductor laser is configured with a double heterostructure,
Its oscillation threshold and temperature characteristics depend on the height of this energy step. In other words, in order to obtain an element that can operate at high temperatures with a low oscillation threshold, this energy step must be sufficiently high. In the case of IILV group semiconductors, the density of states in the conduction band is small, and the conduction band is filled with electrons up to high energy levels, so it is particularly necessary to make ΔEc sufficiently large. In the case of AeGaInP system, InGaAs
Compared to P/InP systems, AeGaAs systems, etc., the distribution ratio of ΔEg to ΔEc is small. This means that InG
This means that even if the same value as ΔEg at the heterojunction in the aAsP/InP system or the AeGaAs system is taken in the AeGaInP system, ΔEc will be smaller than in the former two.

For this reason, in the conventional example, the oscillation threshold was relatively high, and the temperature characteristics were particularly poor, although Eg was sufficiently set.

When increasing the energy gap of the active layer in order to shorten the oscillation wavelength, even if ArInP, which has the largest energy gap, is used as the cladding layer, it is difficult to lower the threshold value and prevent deterioration of temperature characteristics, and the wavelength is 0.60 pm. Low threshold oscillation in the vicinity and continuous operation at room temperature were difficult.

An object of the present invention is to provide a structure of a semiconductor light emitting device that solves the above-mentioned problems.

(Means for Solving the Problem) The gist of the present invention is to provide a semiconductor laser having at least a double heterostructure in which an active layer is sandwiched between cladding layers, in which one of aluminum, gallium, and indium is selected as a group III element. By adopting a double heterostructure in which the active layer and the cladding layer are made of a group IV semiconductor containing part or all of phosphorus as a group V element, and further containing arsenic in the active layer, The object of the present invention is to solve the problems caused by the prior art described above. The current confinement structure may be any other structure such as an internal stripe structure, a planar stripe structure, a buried structure, or the like.

It is not necessarily necessary to take the current narrow 9 structure. Alternatively, a DFB type or DBR type may be used, which has a diffraction grating in the light waveguide region. An important point of the present invention is that arsenic (As) is further added to ArGaInP which becomes the active layer. Simply As
This method becomes even more effective if the composition of other elements is changed while maintaining the lattice constant and bandgap energy. The active layer may be made of GaInP. The manufacturing method for each layer is metal organic pyrolysis vapor phase epitaxial (MOV)
PE) method, molecular beam epitaxial (MBE) method, halogen transport vapor phase epitaxial (HT-VPE) method, liquid phase epitaxial (LPE) method, etc., and any of these methods may be used.

(Function) The height ΔEc of the energy step of the conduction band at the heterojunction interface is defined as the difference in electron affinity of the semiconductor bands constituting the heterojunction, and is uniquely determined.

However, the electron affinity value of III+V group semiconductors, especially their multicomponent mixed crystals, has been unclear. By the way, ΔEc
can be determined as the difference in electron affinity.Conversely, by investigating the properties of the heterojunction using photoelectron spectroscopy, quantum well level measurements, etc., we can find out ΔEc and find out the difference in electron affinity. can.

In other words, although it is difficult to measure electron affinity, the difference can now be known relatively easily, as described above. Also,
Ga□, 5In□, 5P or (ArxGat-x)o, 5In□, 5P (0≦X≦1
), even if As is added as a constituent element, Ae and G
Taking an appropriate value as the composition of a, (AeX' Ga1-
z') yInl-yPl-zAsz (0≦X゛≦1, O
≦y≦1.0≦2≦1), the energy gap value and the lattice constant value can be made equal to the value before adding As. By the way, it has been found that when As is added while satisfying the above-mentioned conditions, the value of electron affinity increases.

In Fig. 2, the energy gap with equal energy gap (Alz'
The Z dependence (As composition dependence) of the electron affinity in Ga□, 5In
□, shown as a relative value to the electron affinity value of 5P.

As shown in the figure, for example, when Eg=1.9eV, Ga
□, 5In□, 5P than (AeO, 2Ga□, B) 0
．． The electron affinity of 7In□, 3P□, 5As□, and 5 is approximately 0.15 eV larger. (Aeo, 5Gao, 4)o
, 5Ino, 5P as the cladding layer, Ga□, 5In
□, ΔEc is 0.1 eV when 5P is used as the active layer, but (Aeo, 2Ga0.8)0.7In0.5P0.
When 5AS0.5 is used as an active layer, ΔEc becomes 0.25 eV. The energy gap of the active layer is equal for both ΔEg
are both 0.4 eV, but ΔEc is larger in the latter. As a result, when a double heterostructure was formed and the oscillation wavelength was 660 nm, (Aeo,
6Gao, 4) 0.5 Ino, active layer with sP as cladding layer (Aeo, 5Gao, 2)o, 7Ino,
The active layer is 5Po, 5Aso, and 5.

The oscillation threshold can be lowered and the temperature characteristics can be made better than those using Ga□, 5In□, and 5P. Also Ae
□, 5In□.

By using 5P as the cladding layer, (AezGai-
x) When 0゜5In0.5P is used as the active layer, the oscillation wavelength is limited to about 600 nm when the active layer is x = 0.3, but if the active layer is (Aro, 45 Gao, 55) o
, 6Ino, 4Po, 5Aso, 2, Δ
Ec = 0.15 eV, ΔEv = 0.05 eV, which makes it possible to oscillate at an oscillation wavelength of about 570 nm (yellow-green) even in continuous operation at room temperature.

(Example) The present invention will be described below using an example. FIG. 1 is a schematic perspective view of an embodiment of the present invention. This is a wavelength of 570
It is a visible light laser that oscillates at nm (yellow-green). n-type G
A layer with a thickness of l is formed on the aAs substrate 1 by MO-VPE method or the like.
pm n-type Ae□, 5In□, 5P cladding layer 2, undoped with a thickness of 0.1 pm (Aeo, 45Gao, 55)
o, 6Ino, 4Po, 5Aso, 2 active layer 3, thickness l
A p-type Ae□, 5In□, 5P cladding layer 4 of 0.5 pm and an n-type GaAs current blocking layer 5 of 0.5 pm are sequentially grown. Next, the width is 2 to 10 pm by photolithography etc.
The n-GaAs block layer 5 is selectively etched and removed only in the striped portions 9 of about 100 mL. Then p-G
An aAs cap layer 6 is grown to a thickness of about 1 pm, and a Ti
A p-electrode 7 made of /Pt/Au and an n-electrode 8 made of Au/Ge are formed on the back surface of the n-GaAs substrate 1. The laser device of this example has an active layer with a wavelength of 570 nm (yellow).
Even if the energy gap is increased until oscillation occurs at ΔEc
is maintained at approximately 0.15 eV, and ΔEv is maintained at approximately 0.05 eV. Therefore, the laser oscillation threshold value is lowered, and the rise in the threshold value due to temperature rise is reduced, so continuous oscillation at room temperature is facilitated and reliability is improved. ArGaIn containing no As
In the P system (Aeo, a5Gao, 5s) o, 5Ino, 5
When trying to obtain an oscillation wavelength of 570 nm using P as the active layer, ΔEc can only be about 0.075 eV, so
Laser oscillation becomes difficult. Therefore, in the embodiment, it is possible to obtain a shorter oscillation wavelength that cannot be obtained with the prior art.

(Effects of the Invention) As described above, by employing the structure of the present invention, an excellent semiconductor laser device with a small oscillation threshold and little characteristic deterioration due to temperature rise can be obtained. Furthermore, as a result, it is possible to obtain a semiconductor laser element having a shorter laser oscillation wavelength than could be obtained with the conventional techniques.

This invention is highly effective in its application to visible light semiconductor lasers, which have been newly opened using new multi-component mixed crystal materials.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of one embodiment of the present invention, and FIG. 2 is a schematic perspective view of (Arx'Ga1-x')yInl-yPl-z
Dependency of electron affinity in Asz on As composition Z. FIG. 3 is a schematic perspective view of a conventional example. In the figure: 1, 51 - n-type GaAs substrate, 2. -n-Ae□, 5
In(1,5P cladding layer 3,... undoped (Aeo, 4sGao, 5s)o
, 6Ino, 4Po, 5Aso, 2 active layer 4, ・=p-A<0.5In□, 5P cladding layer 5
, 55-n-GaAs block layer, 6.56-p-Ga
As cap layer 7.57...p-electrode, 8.58...n electrode 9, 5
9...Current injection stripe region, 52-n-(Ar
□, 5Ga□. s) o, 5Ino, sP cladding layer 53, ... undoped (Aro, xGao, 9) o,
5 Ino, sP active layer 6 - & Fig. 2 0 0, + 0.2 0.3 0.4 0.5 As composition 2

Claims (1)

[Claims] The active layer is a III-V group semiconductor that has at least a double heterostructure in which the active layer is sandwiched between cladding layers, and includes some or all of aluminum, gallium, and indium as the group III element, and phosphorus as the group V element. A semiconductor light emitting device comprising a cladding layer and an active layer further containing arsenic.