JPH0473638B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a compound semiconductor device using an aluminum gallium arsenide (AlGaAs) semiconductor, which is useful for red light emitting diodes, semiconductor lasers, Gunn diodes, phototransistors, etc., and a method for manufacturing the same. <Conventional technology> Light emitting diodes, semiconductor lasers, etc.
Some semiconductor layers use aluminum gallium arsenide, which is a - group compound semiconductor, and in order to have n-type conductivity in the aluminum gallium arsenide layer, tellurium (Te), which is a group element, has traditionally been added as an impurity. Injecting. In addition, this n-type aluminum gallium arsenide layer is generally produced using a liquid phase epitaxial method, in which a solution containing aluminum (Al), gallium arsenide (GaAs), etc. and a trace amount of tellurium is heated at high temperature. After cooling the solution by a certain temperature difference, it is brought into contact with a semiconductor laser substrate, etc., and then slowly cooled.
It is formed by growing crystals. <Problems to be Solved by the Invention> Incidentally, in light emitting diodes, semiconductor lasers, etc., the higher the conduction electron concentration of the n-type semiconductor layer, the lower the resistance of that layer, and the less heat generated by the device during use. As a result, the emission intensity increases, and the performance of the device can be maintained at a good level, such as by suppressing the increase in the laser oscillation threshold current. Moreover, the higher the conduction electron concentration of the n-type layer, the more efficient the electron injection is when a forward voltage is applied, the more active the light-emitting action becomes, and the more the light-emitting efficiency of ordinary light and laser light increases, which is advantageous. Also,
Transistors require emitters with a significantly high electron concentration in order to increase the speed of their functions or to allow large currents. As mentioned above, in various semiconductor devices,
It is desired that the n-type semiconductor layer has a sufficiently high conduction electron concentration. However, none of the conventional compound semiconductor devices having an n-type aluminum gallium arsenide layer satisfactorily meet these demands. One of the reasons for this is the saturation phenomenon of the conduction electron concentration in the n-type aluminum gallium arsenide layer. To explain this saturation phenomenon, the present inventors have developed an n-type aluminum gallium arsenide layer by liquid phase epitaxial method, specifically Al _0.36
When the relationship between the conduction electron concentration of the Ga _0.64 As layer and the Al _0.7 Ga _0.3 As layer and the tellurium concentration in the epitaxial growth solution was investigated, the results shown in FIG. 5 were obtained. From this figure, the conduction electron concentration of the n-type aluminum gallium arsenide layer is 1×
It can be seen that it increases linearly with the addition of impurity tellurium up to around 10 ¹⁸ cm ^-3 , but after that, even if the tellurium concentration is increased, the increase becomes smaller and finally reaches a certain constant value at saturation. for example,
In the case of the Al _0.36 Ga _0.64 As layer, the saturation value of the conduction electron concentration is about 5×10 ¹⁸ cm ^-3 . Therefore, with the conventional manufacturing method of adding only tellurium, there is a certain limit in increasing the conduction electron concentration of the n-type aluminum gallium arsenide layer. was required to be realized. The first object of the present invention is to solve the above-mentioned problems and to provide a compound having an n-type aluminum gallium arsenide layer with a conduction electron concentration at a higher level than before, and which is useful for improving the performance of light emitting diodes, semiconductor lasers, etc. The purpose of the present invention is to provide a semiconductor device. A second object of the present invention is to provide a method for manufacturing a compound semiconductor device that can stably form the n-type semiconductor layer having a high conduction electron concentration. <Means for Solving the Problems> The present inventors have conducted intensive research by changing the types of impurities in order to realize an n-type aluminum gallium arsenide layer with high electron concentration, and in the process, in addition to tellurium as impurities, When germanium (Ge) was added to a gallium solution containing aluminum and gallium arsenide (GaAs) and an n-type aluminum gallium arsenide layer doped with both tellurium and germanium was formed according to a liquid phase epitaxial method, the n-type The layer has an increased conduction electron concentration compared to the case where only tellurium is added, and in particular, the conduction electron concentration is approximately 1×10 ¹⁸
Even in the region exceeding cm ^-3 , the conduction electron concentration increases linearly as the tellurium content increases,
And it was found that it is about 1×10 ¹⁹ cm ^-3 or more. For example, the following enhancement effects were observed.
The present inventors created a tellurium and germanium mixed dope by liquid phase epitaxy by changing the germanium concentration in the gallium solution while keeping the concentration of the added tellurium constant at 1.5 × 10 ^-4 molar fraction. Various n-type Al _0.7 Ga _0.3 As layers were formed and the conduction electron concentrations of these layers were measured. The relationship between the measured conduction electron concentration and the germanium concentration is shown in the graph of FIG. In the figure, the ◯ mark represents the case of the n-type layer, and the broken line (...) represents the level of conduction electron concentration of the Al _0.7 Ga _0.3 As layer without addition of germanium. This figure shows that the conduction electron concentration of the n-type Al _0.7 Ga _0.3 As layer with a tellurium and germanium mixed dope is higher than that without germanium addition, and increases linearly as the amount of germanium added increases. The present inventors completed the present invention based on the above findings. The compound semiconductor device of the present invention is an n-type semiconductor containing tellurium and germanium as impurities.
It has at least one layer of AlxGa _1-x As (0<x<1), and the conduction electron concentration of the n-type semiconductor layer is about 1
×10 ¹⁹ cm ^-3 or more. Further, in the method for manufacturing a compound semiconductor device of the present invention, a solution containing aluminum, gallium, and arsenic and tellurium and germanium added as impurities is prepared at high temperature, and then the solution is applied to the substrate of the compound semiconductor device or its upper surface. The n-type semiconductor layer injected with both tellurium and germanium was made into approximately 1×
AlxGa _1-x with conduction electron concentration greater than 10 ¹⁹ cm ^-3
It is characterized in that the As (0<x<1) layer is formed by a liquid phase epitaxial method. The present inventors conducted further research, and as a result, the conduction electron concentration of an n-type aluminum gallium arsenide layer with a tellurium and germanium mixed dove formed by adding both tellurium and germanium and epitaxially growing according to the manufacturing method of the present invention. However, the conduction electron concentration of a germanium-doped n-type aluminum gallium arsenide layer doped with only germanium and formed in the same manner with the same amount of germanium added, and that of a tellurium-doped n-type aluminum gallium arsenide layer with the same amount of tellurium added and otherwise formed in the same manner. It has been confirmed that the concentration is greater than the sum of the conduction electron concentration of the n-type aluminum gallium arsenide layer of the dove. That is, the present invention utilizes the effect that the conduction electron concentration of the n-type layer increases synergistically due to the mixed doping of tellurium and germanium. Further, germanium is an element conventionally used as an impurity for forming a p-type aluminum gallium arsenide layer. In the method of the present invention, germanium is preferably added to the epitaxial growth solution at a concentration of about 1 x 10 ^-2 mole fraction or less. This is because if germanium is added in excess of this concentration, the surface of the n-type aluminum gallium arsenide layer becomes rough and the crystalline state begins to deteriorate. <Examples> Examples of the present invention will be described below with reference to drawings. Example 1 A compound semiconductor device 1 shown in FIG.
P-type with zinc (Zn) implanted as an impurity on GaAs substrate 2 (conduction hole concentration approximately 3×10 ¹⁸ cm ^-3 )
Al _0.3 Ga _0.7 As layer 3 (layer thickness approximately 2 μm, conduction hole concentration 1
×10 ¹⁸ cm ^-3 ), n with tellurium implanted as an impurity
type Al _0.3 Ga _0.7 As layer 4 (layer thickness approximately 1 μm, conduction electron concentration 3×10 ¹⁸ cm ^-3 ), and n-type Al _0.7 Ga _0.3 As layer 5 with germanium added in addition to tellurium as an impurity.
This is a light-emitting diode in which semiconductors (with a thickness of approximately 3 μm) are laminated in this order, and ohmic electrodes 6a and 6b of gold (Au) alloy are connected to both the upper and lower sides of the laminated semiconductor. The semiconductor device 1 described above is manufactured according to a liquid phase epitaxial method using a slide board. Specifically, the raw materials for each of the gallium solutions for semiconductor layers 3 to 5 are prepared according to the preparation conditions shown in Table 1, and then one or a series of gallium solutions are prepared.

[Table] Separate each in a solution tank in a boat and
The gallium solutions A to C for the semiconductor layers 3 to 5 are prepared by placing them together with the GaAs substrate 2 and then heating them to 800° C. to uniformly melt them. Then 0.3
When the solution A was slowly cooled to 794 °C at a rate of °C/min, the solution A was first brought into contact with the surface of the p-type GaAs substrate to form a zinc-doped p-type Al _0.3 Ga _0.7 As layer 3, and then immediately Shift the boat to remove solution A from substrate 2, then remove solution B from p-type Al _0.3 Ga _0.7
A tellurium-doped n-type Al _0.3 Ga _0.7 As layer 4 is formed on the surface of the As layer 3, and then the solution B is quickly removed, and the solution C is added to the n-type Al _0.3
In contact with the surface of the Ga _0.7 As layer, tellurium is deposited on top of it.
Germanium mixed doped n-type Al _0.7 Ga _0.3 As layer 5
is formed and then solution C is removed. After that,
Electrodes 6a and 6b are attached to the upper surface of the n-type Al _0.7 Ga _0.3 As layer 5 and the lower surface of the p-type GaAs substrate 2, respectively. The semiconductor device 1 is a diode that can be used both as a light emitting element and as a light receiving element. In this device 1, the tellurium and germanium mixed doped n-type Al _Q7 Ga _Q3 As layer 5 includes the zinc-doped p-type Al _0.3 Ga _0.7 As layer 3 and the tellurium-doped n-type Al _0.3 Ga _0.7 As layer forming a p-n junction. Compared to No. 4, the width of the forbidden band is wider, and therefore it is difficult to absorb the light normally absorbed by a pn junction, making it suitable as a window layer for a diode. Moreover, the n-type Al _0.7 Ga _0.3 As layer 5 has a conduction electron concentration of about 1×10 ¹⁹ cm ^-3 , which is much higher than that of the conventional tellurium-doped n-type Al _0.7 Ga _0.3 As layer. Ta. Therefore, the n-type layer can significantly reduce resistance loss and is ideal as a window layer for light emitting diodes and the like. Example 2 The compound semiconductor device 11 shown in FIG.
On a GaAs substrate 12 (conduction electron concentration 1×10 ¹⁸ cm ^-3 ), an n-type Al _0.7 Ga _0.3 As layer 13 (layer thickness approximately 2 μm) doped with germanium in addition to tellurium as an impurity;
Al _0.2 Ga _0.8 As layer 14 without impurity implantation (layer thickness approximately 0.1μ
m), p-type Al _0.7 Ga _0.3 with zinc added as an impurity
As layer 15 (layer thickness 2 μm, conduction hole concentration 1×10 ¹⁸ cm
^-3 ), and n-type with tellurium added as an impurity
GaAs layers 16 (layer thickness approximately 0.5 μm) are laminated in this order, and zinc diffusion is applied to the n-type GaAs layer 16.
The semiconductor laser has a double heterostructure in which a shaped region 17 is formed and gold alloy ohmic electrodes 18a and 18b are connected to both upper and lower sides of the laminated semiconductor. The above semiconductor device 11 is also manufactured according to the liquid phase epitaxial method using a slide board.
Specifically, first, each raw material for the gallium solution for the semiconductor layers 13 to 16 is prepared according to the preparation conditions shown in Table 2, and then one or a series of raw materials are prepared.

[Test example]

The present inventors kept the germanium concentration in the epitaxial growth solution constant at 5 x 10 ^-3 molar fraction while changing the amount of tellurium added to the solution.
tellurium, germanium mixed doped n-type aluminum gallium arsenide Al _x Ga _1-x As (o<x<1) layer;
Specifically, the Al _0.7 Ga _0.3 As layer and the Al _0.36 Ga _0.64 As
Various semiconductor devices having layers were manufactured in the same manner as in Examples 1 and 2, and then the conduction electron concentration of the n-type aluminum gallium arsenide layer of each device was measured. The results are shown in FIG. In the figure, the ◯ marks represent the case of an n-type aluminum gallium arsenide layer mixedly doped with tellurium and germanium, and the ● marks represent the case of a conventional n-type aluminum gallium arsenide layer not implanted with germanium. From this figure, the n-type aluminum gallium arsenide layer mixedly doped with tellurium and germanium does not become saturated even when the conduction electron concentration exceeds around 1×10 ¹⁸ cm ^-3 and increases linearly.
It can be seen that this is significantly different from the case of a conventional n-type layer without germanium implantation, which is saturated. Moreover,
All of the mixed doped n-type layers had a good crystalline state. <Effects of the Invention> As explained above, the compound semiconductor device of the present invention overcomes the saturation phenomenon of the conduction electron concentration by injecting germanium in addition to tellurium as an impurity into the aluminum gallium arsenide layer. This results in the formation of an n-type aluminum potassium arsenide layer, which has a higher level of than conventional methods, such as approximately 1×10 ¹⁹ cm ^-3 or more, making it possible to provide high-performance diodes, semiconductor lasers, and the like. In addition, in the method for manufacturing a compound semiconductor device of the present invention, germanium and tellurium are added to a liquid phase epitaxial solution for epitaxial growth, so that the conduction electron concentration is about 1×10 ¹⁹ cm ^-3 or more. An n-type aluminum gallium arsenide layer can be stably formed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a compound semiconductor device according to Example 1 of the present invention, FIG. 2 is a cross-sectional view showing a compound semiconductor device according to Example 2, and FIG. 3 is a cross-sectional view showing a compound _{semiconductor} device according to Example ₂ of the present invention.
Fig. 4 shows the relationship between the conduction element concentration and the added germanium concentration for a tellurium-doped n-type Al _0.3 Ga _0.3 As layer. FIG. 5 is a diagram showing the relationship between the conduction electron concentration and the added tellurium for a conventional n-type Al _x Ga _1-x As (o<x<1) layer doped solely with tellurium. In the figure, 1, 11... compound semiconductor device, 5, 1
3...N-type injected with tellurium and germanium
Al _0.7 Ga _0.3 As layer.

Claims (1)

[Claims] 1. At least one layer of n-type semiconductor Al _x Ga _1-x As (0<x<1) containing tellurium and germanium as impurities, and the conduction electron concentration of the n-type semiconductor layer is approximately 1×10 ¹⁹ cm ^-3 or more. 2. A solution containing aluminum, gallium, and arsenic and to which tellurium and germanium are added as impurities is prepared at a high temperature, and then the solution is cooled by a certain temperature difference, and then brought into contact with the surface of a compound semiconductor substrate, followed by slow cooling. The n-type semiconductor layer doped with both tellurium and germanium is approximately 1×10 ¹⁹ cm.
Al _x Ga ¹ _-x As (0<
A method for manufacturing a compound semiconductor device, characterized in that a layer (x<1) is formed by a liquid phase epitaxial method.