JPH0250617B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for manufacturing a semiconductor device, and it is possible to produce different carrier concentrations in a single solution by controlling the carrier concentration during liquid phase epitaxial growth. This provides a liquid phase epitaxial growth method that allows the formation of three layers.

Conventional configurations and their problems Gallium phosphide (GaP) light-emitting diodes, which mainly emit nitrogen (N), are currently widely used as green light-emitting diodes, but their light-emitting efficiency is generally lower than that of other light-emitting diodes. It's low. FIG. 1 is a cross-sectional view of a conventional GaP green light emitting diode. What is shown in the same figure is an n-type GaP substrate 1 on which an n-type
It has a structure in which a GaP epitaxial layer 2 is formed, a p-type GaP epitaxial layer 3 is formed thereon, and n- and p-side electrodes 4 and 5 are provided. In this structure, it is known that reducing the carrier concentration of the n-type epitaxial layer 2 reduces the adverse effect of free donors and improves the luminous efficiency.

FIG. 2 shows the dependence of the effective efficiency on the n-carrier concentration experimentally obtained. For high efficiency, n
The epitaxial layer 2 must have a low concentration of less than 10 ¹⁷ cm ^-3 . On the other hand, when the carrier concentration of the n-type epitaxial layer 2 is reduced to 5×10 ¹⁶ cm ^-3 or less, a part of the n-type epitaxial layer 2 near the interface with the n-substrate 1 is reversed to p-type. This tendency occurs. This is due to the influence of residual acceptors in the boat. From this background, conventionally, there is a limit to the reduction in the donor concentration of the n-layer 2 in order to improve efficiency. Therefore, a structure as shown in FIG. 3 is generally used. This structure is n-type
An n-layer 7 with a concentration of 2×10 ¹⁷ cm ^-3 or more is formed on the GaP substrate 6 to prevent the formation of the p-inversion layer described above, and a layer 7 with a concentration of 5×10 ¹⁶ cm ^-3 or less as described above is formed. A low concentration n-type GaP epitaxial layer 8 is then formed.
A p-type GaP epitaxial layer 9 is formed. In order to manufacture such a structure, it is necessary to prepare three solutions using the usual liquid phase epitaxial growth method, which is disadvantageous in terms of economy and the complexity of the boat structure, which makes mass production difficult. There was a drawback.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned drawbacks and provides a liquid phase epitaxial growth method that allows the formation of three layers with different carrier concentrations using a single solution.

Structure of the Invention The present invention includes a first step of bringing a solution containing a predetermined composition into contact with a substrate to perform liquid phase epitaxial growth, and then reducing the concentration of doping impurities in the solution by reducing pressure. A second step of growth using this solution again, and a doping impurity of a conductivity type opposite to that of the gas phase is put into the solution, and then growth is performed using this solution, and the growth is performed in the first and second steps. a third step of forming a layer of a conductivity type opposite to that of the first layer, which uses a single solution and reduces the concentration of doping impurities therein. In addition, the process of changing the conductivity type is controlled by a vapor phase control method, thereby making it possible to realize a highly efficient light emitting semiconductor device.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a schematic diagram of a manufacturing apparatus used in the liquid phase epitaxial growth method of the present invention. Quartz reaction tube 1
Acceptor impurity metal 1 at one end 11 of 0
A boat 14 having one solution tank is installed in the central part 13, and the other end 15 of the reaction tube 10 is connected to a pump 16, so that the inside of the reaction tube can be brought into a reduced pressure state. In addition, the reaction tube 10 is in the region 1
Heating bodies 20 and 21 are arranged so that the temperatures of 1 and 13 can be controlled independently.

First, an n-type GaP substrate 23 of 3×10 ¹⁷ cm ^-3 is installed in the substrate holder 17 in the boat, and a solution 19 is placed in the solution tank 18.
Put in. The liquid composition is 20g of gallium (Ga), 500mg of polycrystalline GaP, and tellurium (Te) as a donor impurity.
It is 60μg. This liquid was placed in a hydrogen atmosphere (1 atm).
After heating at 1030° C. and leaving for 60 minutes to fully dissolve, it is brought into contact with the substrate 23. After being left in contact for 30 minutes, the substrate 23 is cooled to 950° C. at a rate of 1° C./min to form an n-type epitaxial layer on this substrate 23.
The electron carrier concentration is 2×10 ¹⁷ cm ^-3 and the thickness is 22 μm.
It is. Next, cooling is stopped at 950° C., the solution 19 is maintained at a constant temperature, and the inside of the reaction tube is evacuated by the pump 16 to reduce the pressure to 0.05 Torr. Under this condition,
The donor impurity Te in the solution evaporates, and the
Te concentration decreases. Of course, the concentration changes depending on the reduced pressure, temperature, time, etc., so it is necessary to understand the selection conditions in advance.

Next, the inside of the reaction tube is changed to a hydrogen atmosphere of 1 atm again, and cooling is started again at a rate of 1.0° C./min. When cooled to 900° C., an n-type epitaxial layer 8 of 30 μm is formed. Here, as mentioned above, in solution 18
Since the Te concentration has decreased, the electron carrier concentration of the n-type epitaxial layer 8 has decreased to about 4×10 ¹⁶ cm ^-3
It has become a degree. When the temperature in the central region 13 of the reaction tube reaches 900°C, one end 1 of the reaction tube
The temperature of one region is raised to 600° C., and the acceptor impurity metal zinc (Zu) 12 is evaporated. As a result, Zu diffuses into the solution 19, and the solution 19 becomes doped with Zn. Therefore, by continuing to cool from 900°C to 800°C at a rate of 1°C/min, the resulting epitaxial layer is doped with Te and Zn, and becomes p-type because the Zn concentration is higher than the Te concentration. The hole carrier concentration is 1×10 ¹⁸ cm ^-3 and the thickness is
It is 20 μm.

Effects of the Invention As described above, the present invention creates a reduced pressure state during the liquid phase epitaxial growth process and reduces the amount of impurities in the solution, thereby making it possible to fabricate epitaxial layers with different carrier concentrations using one solution. ,
In addition, the impurity is compensated for by doping the impurity into the solution rather than the gas phase, and a layer having a conductivity type different from the epitaxial layer is formed.
Layers with different carrier concentrations can be produced using a single solution, making it extremely advantageous in terms of mass production and economy.

Although the GaP green light emitting diode has been described here, it is clear that the present invention can also be applied to liquid phase epitaxial growth of other semiconductors.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a normal GaP green light-emitting diode, Figure 2 is a diagram of the relationship between luminous efficiency and carrier concentration in the n-layer, Figure 3 is a cross-sectional view of a high-efficiency GaP green light-emitting diode, and Figure 4 is a diagram of the relationship between luminous efficiency and n-layer carrier concentration. 1 is a conceptual diagram of a manufacturing apparatus used in the invention. 6...GaP substrate, 7...High concentration n-type GaP epitaxial layer, 8...Low concentration n-type GaP epitaxial layer, 9...P-type GaP epitaxial layer, 10...
... Reaction tube, 11 ... End of reaction tube, 12 ... Acceptor impurity metal zinc, 13 ... Center part of reaction tube, 14 ... Boat for liquid phase epitaxial growth,
15...exhaust port, 16...pump, 17...GaP
Substrate, 18...solution tank, 19...solution.

Claims (1)

[Claims] 1. A first step of bringing a solution containing a predetermined composition into contact with a semiconductor substrate for liquid phase epitaxial growth;
Thereafter, the concentration of the doping impurity in the solution is reduced by reducing the pressure, and then the solution is used again for liquid phase epitaxial growth. After introducing the solution into the solution, a third step of forming a layer of a conductivity type opposite to that of the liquid phase epitaxial growth layer formed in the first and second steps using the solution. Method.