JPH0464456B2

JPH0464456B2 -

Info

Publication number: JPH0464456B2
Application number: JP28156384A
Authority: JP
Inventors: Hiroyuki Kano; Masafumi Hashimoto
Original assignee: Toyota Central R&D Labs Inc
Current assignee: Toyota Central R&D Labs Inc
Priority date: 1984-12-29
Filing date: 1984-12-29
Publication date: 1992-10-15
Also published as: JPS61159725A

Description

[Brief explanation of drawings]

第１図および第２図は本発明の液相成長法によ
るGeドープAlyGa_1-yAsの特性を示すグラフ、第
３図Ａ，Ｂは本発明の液相成長の一実施例を示す
グラフアイトボートの断面図、第３図ＣはGa溶
液の加熱方法の一例を示すグラフ。第４図は本発
明の一実施例により成長した結晶の断面模式図、
第５図Ａ〜Ｃは本発明の液相成長の他の実施例を
示すグラフアイトボートの断面図、第６図は本発
明の他の実施例により成長した結晶の断面模式
図、第７図は従来のAlGaAsのｐ−ｎ接合を説明
するための結晶の断面模式図である。図中、１１……ｎ形GaAs基板、１２……ｎ形
AlxGa_1-xAs層、１３……Zn拡散によりできたｐ
形AlxGa_1-xAs層、１４……ｐ形AlyGa_1-yAs層、
１５……ｐ−ｎ接合界面、１６……当初のｐ形層
とｎ形層の接合界面、３０，５０……グラフアイ
トボート、３１，５１……ふた、３２，５２……
スライダ、３３，５３……基板ホルダー、３４，
５４−１，５４−２……Ga溶液、３５，５５…
…基板、３６，５６，５７……成長したAlGaAs
層。 Figures 1 and 2 are graphs showing the characteristics of Ge-doped AlyGa _1-y As produced by the liquid phase growth method of the present invention, and Figures 3A and B are graphite graphs showing an example of the liquid phase growth method of the present invention. A cross-sectional view of the boat, and FIG. 3C is a graph showing an example of a method of heating a Ga solution. FIG. 4 is a schematic cross-sectional view of a crystal grown according to an embodiment of the present invention;
5A to 5C are cross-sectional views of graphite boats showing other embodiments of liquid phase growth of the present invention, FIG. 6 is a schematic cross-sectional view of crystals grown according to other embodiments of the present invention, and FIG. 7 is a schematic cross-sectional view of a crystal for explaining a conventional p-n junction of AlGaAs. In the figure, 11... n-type GaAs substrate, 12... n-type
AlxGa _1-x As layer, 13...P formed by Zn diffusion
Type AlxGa _1-x As layer, 14...p type AlyGa _1-y As layer,
15... p-n junction interface, 16... original p-type layer and n-type layer bonding interface, 30, 50... graphite boat, 31, 51... lid, 32, 52...
Slider, 33, 53...Substrate holder, 34,
54-1, 54-2...Ga solution, 35,55...
...substrate, 36,56,57...grown AlGaAs
layer.

Claims

[Claims] 1. A substrate having a p- or n-type Al _y Ga _1-y As (0≦y<1) layer containing germanium (Ge) as an impurity and containing aluminum (Al) and arsenic (As).
In liquid phase growth of a crystal layer on the substrate by contacting with a gallium (Ga) solution containing p-type Al _y Ga ₁ on the substrate, by appropriately changing the amount of Al in the gallium solution. _-y As(0≦y
<1) layer or n-type Ae _x Ga _1-x As (0<x<1)
A compound semiconductor liquid phase growth method characterized by growing a layer (where x and y have a relationship of 0≦y<X<1) in a liquid phase. 2. On the substrate, a p-type Al _y Ga _1-y As (0≦y<1) layer and an n-type Ae _x Ga _1-x As (0<x<1) layer are continuously grown in liquid phase. The compound semiconductor liquid phase growth method according to claim 1, characterized in that a pn junction is formed. [Scope of Claims] [Industrial Application Field] The present invention relates to a method for producing an aluminum gallium arsenide compound semiconductor, which is useful for semiconductor lasers and the like, by a liquid phase growth method. [Prior art] Gallium arsenide (GaAs), aluminum (Al), and impurities are dissolved in a molten gallium (Ga) solution at high temperature to create a saturated solution of aluminum gallium arsenide (AlGaAs), and this saturated Ga solution is used to dissolve GaAs or In the compound semiconductor liquid phase epitaxy method, in which AlGaAs crystals are grown by contacting the AlGaAs substrate with slow cooling, conventionally only p-type AlGaAs was formed when germanium (Ge) was used as an impurity dissolved in the Ga solution. I couldn't do it. In the liquid phase growth method of compound semiconductors, to form a p-n junction, it is generally formed from a solution to which p-type impurities and n-type impurities are added, or an amphoteric material that exhibits both p-type and n-type conductivity is used. There is a method of forming it by adding impurities, and silicon (Si) and Ge are considered to be amphoteric impurities in the GaAs liquid phase growth method. However, in the case of AlGaAs, Ge
As mentioned above, it was conventionally thought that only p-type was formed. On the other hand, in the liquid phase growth method of GaAs, as an impurity
By using Si, n-type GaAs and p-type
By growing GaAs and forming a p-n junction with the same impurities, a high-quality p-n junction is created in which the p-n junction interface does not move even during liquid phase growth or during high-temperature treatment after growth. was formed as designed. However, in the liquid phase growth method of AlGaAs containing Al, the impurity Si exhibits p-type and n-type, but it is not actually used because it does not result in a high carrier concentration. For the above reasons, conventional AlGaAs homo p-n junctions and hetero p-n junctions are formed by liquid phase growth using a method using n-type impurities and p-type impurities. As shown in FIG. 7, this method involves epitaxially growing an n-type AlGa _{1-x As layer 12 doped with n-type impurity Te on an n-type GaAs substrate 11, and then growing a p-type AlGa 1-x} As layer 12 doped with p-type impurity Zn on an n-type GaAs substrate 11. shape
The AlyGa _1-y As layer 14 is also epitaxially grown. However, during the crystal growth of the p-type AlxGa _1-y As layer 14, impurity Zn moves due to diffusion, and the p-n junction surface moves from the original junction surface 16 into the n-type AlxGa _1-x As layer 12. Moving. The moved joint surface 15 is shown by a broken line. For this reason, n-type
The hetero interface 16 between the AlxGa _1-x As layer 12 and the p-type AlyGa _1-y As layer 14 and the pn junction interface 15 are misaligned. This phenomenon is a problem when you have a heterojunction where x≠y, and you thought you were creating a heteropn junction, but in reality it is p
Type AlxGa _1-x As layer 13 and n-type AlxGa _1-x As layer 12
Since it becomes a homo p-n junction with , the carrier confinement effect and minority carrier injection efficiency decrease when used as a light emitting device, resulting in poor luminous efficiency. In the case of transistors, if Zn-doped p-type AlGaAs is used as the base, n-type emitter,
Zn is diffused to the collector side and the base width becomes wider.
A problem arises in that the frequency characteristics deteriorate. [Problems to be solved by the invention] In the above, if the same impurity such as Ge is used as the p-type and n-type impurities, the diffusion coefficient will be small, and since the p-type or n-type changes depending on the Al composition, the p-n This shows the advantage that there is almost no movement of the bonding interface due to heat treatment. The present invention uses the same impurity Ge to produce p-type
AlyGa _1-y As (0≦y<1) and n-type AlxGa _1-x As
A high-quality p-n junction can be formed as designed, in which a p-n junction (0 < x < 1) can be formed, and the formed p-n junction interface does not move during liquid phase growth or during post-growth heat treatment. The object of the present invention is to provide a liquid phase growth method for forming compound semiconductors. [Means for solving the problem] The present inventors focused on the Ge impurity conventionally used to make p-type AlGaAs, and as a result of conducting detailed doping experiments with the impurity,
In the liquid phase growth method of AlGaAs, the crystal growth temperature,
When the amount of Ge added to the Ga solution is kept constant, Al
The present invention was completed by discovering that as the amount of added AlyGa _1-y As, that is, y of the growing AlyGa _{1-y As increases, the growing AlyGa 1-y} As changes from the conventionally known p-type to n-type. That is, in the liquid phase growth method of compound semiconductors of the present invention, a substrate having a p- or n-type Al _y Ga _1-y As (0≦y<1) layer is grown using aluminum (Al) containing germanium (Ge) as an impurity. and arsenic (As)
In liquid phase growth of a crystal layer on the substrate by contacting with a gallium (Ga) solution containing p-type Al _y Ga ₁ on the substrate, by appropriately changing the amount of Al in the gallium solution. _-y As(0≦y
<1) layer _or n-type _Al Features. The liquid phase growth method of the present invention uses a GaAs substrate or
n-type AlxGa _1-x As (0<x<1) on AlGaAs substrate
A p-type layer may also be formed on the substrate.
AlyGa _1-y As (0≦y<1) layer with n-type AlxGa _1-x As
(0<x<1) layer may be formed, and further p-
P-type and n-type may be formed in multiple stages so that a plurality of n-junctions are formed. The present invention will be explained in more detail below. Conventionally, when p-type AlyGa _1-y As was obtained using a liquid phase growth method, about 0.01 g of Ge was added to 1 g of Ga in a Ga solution (molten liquid) containing a predetermined amount of GaAs and Al. The present inventors developed conditions in which the amount of Ge added was smaller than before, for example, 0.005 g per 1 g of Ga.
Or, when it is 0.002g, AlyGa _1-y As
was grown on a GaAs substrate in a liquid phase at a saturation temperature of 800°C with various Al compositions, that is, the value of y. As shown in Figure 1, even with the same amount of Ge added, the Al composition y increased. In other words, when the amount of Al added to the Ga solution is increased, crystal growth occurs.
We found that AlyGa _1-y As changes from the conventionally known p-type to the n-type, which has not been formed until now. The value of y of this p, n inversion decreases as the amount of impurity Ge added decreases. As shown in FIG. 1, when Ge is 0.002 g, the mole fraction of AlAs is smaller than when the amount added is 0.005 g. Furthermore, as shown in FIG. 2, when the amount of Ge added to the Ga solution is kept constant, the value of y for p, n inversion decreases as the saturation temperature increases. Note that since the saturation temperature is approximately equal to the crystal growth temperature, it may be considered as the growth temperature. In the liquid phase growth method described above, from the growth characteristics of AlyGa _1-y As with Ge added as an impurity, it is possible to determine the amount of Ge added and the amount of Al added in the Ga solution, as well as the saturation temperature of the Ga solution (approximately the growth temperature). By selecting the conditions (equal to ), it is possible to grow n-type and p-type AlyGa _1-y As by adding the same impurity Ge. As can be seen from the above explanation, p-type AlyGa _1-y
As (0≦y<1) and n-type AlxGa _1-x As (0<x<
In 1), X and y have a relationship of 0≦y<x<1. The amount of Ge added to the Ga solution is not particularly limited, and may be added in an amount of 0.01g per 1g of conventional Ga, but preferably in the amount of 0.001 to 0.008g, p, n
Reversal is clearly observed. As can be seen from the results in FIG. 1, by changing the amount of Ge added between the n-type layer and the p-type layer, a homopn junction of AlyGa _1-y As is also possible. According to the present invention, p-type AlyGa _1-y As and n-type
By continuous liquid phase growth of AlxGa _1-x As, p-n
A bond can be formed. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. Example 1 A GaAs substrate 3 is placed in a graphite boat 30 consisting of a lid 31, a slider 32 with a Ga solution reservoir, and a substrate holder 33 as shown in FIG. 3A.
5 and Ga1g, GaAs0.018g, Al0.0026g,
First, a raw material consisting of 0.002 g of Ge was introduced and heated under a temperature program as shown in Figure 3C in an H ₂ gas atmosphere.
The temperature was raised to T ₁ = 830℃ to dissolve the raw material in Ga.
A Ga solution 34 is prepared, and then the temperature is lowered to T ₂ =800° C. to obtain a saturated Ga solution. Afterwards, this 800
Start slow cooling from ℃ at a rate of ΔT = 0.3℃/min,
When the temperature has dropped a few degrees Celsius, operate the slider 32 to
As shown in FIG. 3B, the Ga solution 34 is applied to the GaAs substrate 3.
5, supersaturated AlyGa _1-y As (y
=0.7) layer 36 is grown on substrate 35. After growing the layer 36 to a suitable thickness (3 to 5 μm) in this manner, the Ga solution is removed by the slider 34, for example by returning to the arrangement shown in FIG.
After cooling, the substrate 35 is taken out. The crystals thus formed are as shown in Figure 4.
It has an n-type (n=1.5×10 ¹⁷ cm ⁻³ ) AlyGa _1-y As (y=0.7) layer 36 epitaxially grown on a GaAs substrate 35 . In this example, the substrate 3
5 is not limited to GaAs but p-type AlyGa _1-y As (0<y<
1) is also acceptable. Embodiment 2 FIG. 5 is a diagram showing another embodiment of the present invention, in which a graphite boat 5 consisting of a lid 51, a slider 52 with a Ga solution reservoir, and a substrate holder 53 is shown.
0, p-type GaAs substrate 55, Ga solution 54-1 (Ga1
g, GaAs0.037g, Al0.00048g, Ge0.002g), Ga solution 54-2 (Ga1g, GaAs0.0018g)
g, Al0.0026g, Ge0.002g) was first heated in _H2 according to the temperature program shown in Figure 3C.
Ga solutions 54-1 and 54-2 are prepared by raising the temperature to T ₁ =830° C. and dissolving the raw material in Ga. Next, the temperature is lowered to T ₂ =800°C to form a saturated Ga solution. After that, slow cooling is started from 800°C at a rate of ΔT = 0.3°C/min, and when the temperature has dropped by several degrees, the slider 52 is operated to first deposit the Ga solution 54-1 onto the p-type GaAs substrate 55. When contacted as shown in Figure 5B, supersaturated AlyGa _1-y As (y=0.2)
A layer 56 is grown on substrate 55. Next, after the layer 56 has grown to an appropriate thickness (for example, several μm), the slider 52 is operated to apply the Ga solution 54-2 to the
When AlyGa _1-y As layer 56 is contacted as shown in FIG. 5C, a supersaturated AlxGa _1-x As (x=0.7) layer 57 grows on said layer 56. After layer 57 has grown,
Apply the Ga solution 54-2 from above the layer 56 to the slider 52.
After cooling, the substrate 55 is removed. As shown in FIG. 6, the crystal thus formed is a p-type (p=3×10 ¹⁷ cm ^-3 ) AlyGa _1-y As (y
= 0.2) layer 56 and n-type (n = 1.5×10 ¹⁷ cm ^-3 )
A layer having a hetero pn junction 58 of an AlxGa _1-x As (x=0.7) layer 57 is formed. In the crystal obtained above, according to measurement using an electron microscope, the hetero interface and the pn junction interface were in good agreement. The above is an example of two layers grown as crystals, but
It is also possible to grow multiple layers in the same way. [Effect] In the present invention, by adding one type of impurity Ge, p-type and n-type AlGaAs crystals can be formed by a liquid phase formation method.
It is possible to form a heterojunction between AlxGa _1-x As and p-type AlyGa _1-yAs and a designed heterojunction in which the pn junction interface matches. This means that even in semiconductor lasers, light-emitting diodes, light-emitting devices, and transistors that have hetero p-n junctions using combinations such as AlGaAs/GaAs and AlGaAs/AlGaAs, the p-n junction position can be maintained even during and after crystal growth during high-temperature treatment. Since the position of the heterojunction does not change, highly efficient minority carrier injection and highly efficient carrier confinement are possible, resulting in higher luminous efficiency in light emitting devices, lower dark current in light emitting devices, and higher amplification in transistors. rate and frequency can be increased. For example, in the conventional example shown in FIG. 7, a diode is formed in which the position of the heterojunction and the position of the pn junction are shifted. For this reason, the injection efficiency of electrons into the p-type layer is increased by a hetero p-n junction, but in the conventional example, it becomes a homojunction, so the injection efficiency cannot be improved and the luminous efficiency decreases when used as a light emitting diode. It doesn't rise. In contrast to the above, in the hetero p-n junction according to the present invention shown in FIG. 6, since the hetero junction interface and the p-n junction interface coincide, the injection efficiency of minority carriers can be increased as designed, and the light emitting diode When this is done, luminous efficiency can be improved. As mentioned above, in the present invention, one type of impurity
By using Ge, a p-n junction can be obtained,
Furthermore, since this pn junction is stable, the various excellent effects described above are achieved.