JPS6390142A - Method of doping impurity into semiconductor material - Google Patents

Abstract

PURPOSE:To realize the manufacture of P-type ZnS by a method wherein, by thermally diffusing a semiconductor at a high temperature, an impurity is introduced into a regular lattice position and into a position other than that and a dopant located at an intrusion-type position is shifted by jointly using heat and an electric field so that the dopant located at a position other than the regular position can be exfoliated. CONSTITUTION:After a ZnS bulk crystal 1 has been immersed in a lithium sulfate aqueous solution, it is taken out and dried. This crystal 1 coated with lithium sulfate and a ZnS powder 3 to be used for prevention of pyrolysis of a crystal are put in a clean quartz ampule 2, which is then vacuum-sealed. Then, after the ampule 2 has been put in an electric furnace 4 and has been heated, the ampule 2 is broken and the crystal 1 is taken out. A bulk crystal 10, where W electrodes 8, 9 are attached to its both sides and are connected to an external power source 16, and a ZnS powder 11 are again put in an ampule 7. After that, the ampule 7 is put in an electric furnace 7 and is heated. At the same time, an electric field is given to the bulk crystal 10 by means of the electrodes 8, 9 and a dopant located at an intrusion-type position is shifted and is rearranged to a regular position. As a result, a dopant layer which remains at a position other than the regular position is exfoliated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of doping semiconductor materials with impurities.

[Conventional technology]

Impurity doping into a semiconductor is the most important process for manufacturing semiconductor devices, and device creation is impossible without impurity doping. However, for semiconductor materials with a large forbidden band width, it is currently not possible to freely dump them into n-type and p-type.
For example, for Zn5 (zinc oxide) used in the present invention, there is no doping method that can provide a p-type with low resistance.

[Problem that the invention seeks to solve]

As already mentioned, n-type and p-type doping cannot be easily achieved in semiconductor materials with a large forbidden band width.This is because the forbidden band energy is large compared to the defect generation energy in the matrix induced by doping. The reason for this is that (1) during doping, defects (for example, vacancies in the host constituent element, etc.) with a charge opposite to that of the dopant substituted at the normal position are generated due to the self-compensation effect (Cseef-compensation). 2)
During doping, an automatic compensation effect (au jo-co
When the same dopant is substituted at an interstitial position (for example, when the same dopant is substituted at an interstitial position), it is
It is believed that this is due to the occurrence of defects (defects present in 5ite). ZnS (zinc sulfide) specifically treated in the present invention
In the case of doping Li with Li, it is considered that p-type crystals cannot be formed due to the reason (2) above. The impossibility of p-type doping is a fatal flaw in this type of semiconductor device, which is expected to emit light or operate as a laser diode through a pn junction.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for doping impurities into semiconductor materials that can easily achieve n-type and p-type doping even in semiconductor materials with a large forbidden band width. .

[Means for solving problems]

The method of doping impurities into semiconductor materials of the present invention involves first doping impurities into regular lattice positions and other positions in the semiconductor by thermal diffusion at high temperatures, and then doping the impurities into the semiconductor by diffusion using both heat and an electric field, such as by an automatic compensation effect. Only the dopant impurities at the interstitial positions that have been generated are diffused and moved to form a layer in which only the dopants substituted at the regular positions are present, and the layer containing the dopant impurities, etc. located at positions other than the regular lattice positions that have been generated by diffusion is further peeled off. In this way, a layer is obtained in which only the substituted dopant exists at the intended regular position.

[Effect]

It is well known that when a certain type of impurity is diffused into a certain type of semiconductor, the impurity replaces the normal position of the parent body and at the same time is located at the interstitial position. This often occurs when the impurity atoms that try to diffuse are smaller than the host atoms, and Li in ZnS, Li in GaP (gallium chloride), Li in St and Ge, etc. described in this invention are well known. It is being On the other hand, an interstitial impurity in a semiconductor has a smaller energy barrier for diffusion than a substitutional impurity, and if ionized, it can be easily diffused by an electric field. Therefore, if an electric field is applied to a semiconductor simultaneously containing substitutional impurities at interstitial sites at an appropriate temperature, only the interstitial impurities with a small diffusion energy barrier will diffuse to one side of the electrode, forming a layer containing only substitutional impurities. can be formed.

In the impurity diffusion according to the present invention, irrespective of the type of host semiconductor and the type of impurity atoms used, defect levels of opposite sign (for example, donor level and acceptor level, etc.) generated by high-temperature thermal diffusion, and also due to external causes. This can be applied if there is a difference in the diffusion energy barrier (including intrinsic defect levels), and it is not possible to cover all cases here.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are principle diagrams of steps shown in order to explain an embodiment of the present invention, and FIG. 1 shows step 1. FIG. 2 is an explanatory diagram of step 2. In this example, Zn
A method for obtaining a P-type crystal by diffusing Li into S will be explained.

First, in step 1, about 20 grams of lithium sulfate is
Dissolve it in gram of water to make a lithium sulfate aqueous solution. A ZnS bulk crystal 1 cut into 10 x 101 x 1 pieces and etched with a chromium mixed acid solution and a potassium hydroxide aqueous solution (30%, 90°C) is immersed in this aqueous solution, then taken out and dried at about 110°C. At this time, the ZnS bulk crystal 1, which has been coated with this lithium sulfate aqueous solution and dried, is added to a quartz ampoule 2 that has been thoroughly washed and thoroughly washed to prevent other impurities from being mixed in. After putting in the ZnS powder 3 as shown in FIG. 1, the quartz pulley 2 is connected to a high vacuum evacuation device. ZnS
Evacuate the quartz ampoule 2 so that the powder 3 does not spread, and
The quartz ampoule 2 is sealed when the ultra-high vacuum below TOrr is reached.Then, the entire quartz ampoule 2 is placed in an electric furnace 4 and heated to Z by heating heaters 5 and 6, respectively.
The nS bulk crystal 1 and the ZnS powder 3 are arranged so as to be heated independently. After the above operation, current is applied to the heaters 5 and 6. The temperature for this high-temperature thermal diffusion of Li,
Although the time depends on various conditions, in the case of this example, Zn
The temperature of the S bulk crystal 1 was set at 850°C and the temperature of the ZnS powder 3 was set at 870°C, and maintained for 5 hours. After the above heat treatment, the quartz ampoule 2 is broken and the ZnS bulk crystal 1 is taken out, and after etching with an aqueous potassium hydroxide solution (30%, 90° C.), tungsten metal is deposited on both sides of the crystal. A III-phi platinum wire is crimped onto this tungsten metal.

Next, in step 2, as shown in FIG. 2, a ZnS bulk film, which has been previously diffused with Li in step 1 and has tungsten metal electrodes 8 and 9 on both sides of the crystal, is placed in a thoroughly cleaned quartz ampoule 7. A platinum wire 1 drawn out from tungsten metal electrodes 8 and 9 is placed with a crystal 10 and ZnS powder 11 added to prevent thermal decomposition of the crystal.
2 and 13 are connected to through electrodes 14 and 15 that have been attached to the quartz ampoule 7 in advance, and the through electrodes 14 and 15 are further connected to a power source 16 placed outside the quartz ampoule 7, and the entire quartz ampoule is connected to an electric furnace 17. ZnS is heated by independent heaters 18 and 19 arranged in
The bulk crystal 10 and the ZnS powder 11 are arranged so as to be heated independently.

Among the above operations, current is passed through the heaters 18 and 19. The temperature, time, voltage of the power supply 16, etc. for this electric field and thermal diffusion of Li depend on various conditions, but in the case of this example, the temperature of the ZnS bulk crystal 10 was set to 320°C,
The temperature of the ZnS powder 11 was set to 400° C., the voltage was set to 1000 pol h, and this was maintained for 30 hours.

In the subsequent step 3, the quartz ampoule 7 is broken, the ZnS bulk crystal 10 is taken out, and a potassium hydroxide aqueous solution (30
%, 90° C.) to remove the high resistance layer present on the front or back surface.

Hall measurements at room temperature revealed that ZnS after the above operations
As a result of evaluating the hole concentration of the bulk crystal, the Hall coefficient was positive, that is, p-type, and the carrier concentration was I
It was 17 cm. In addition, Hall measurement was impossible for samples subjected to only high-temperature thermal diffusion of Li (Steps 1 and 3) due to high resistance.

In this example, ZnS is used as the semiconductor, and L is used as the impurity.
However, as mentioned in the section on effects, regardless of the type of host semiconductor and the type of impurity atoms used, defect levels of opposite sign (for example, donor level and acceptor level) generated by high-temperature thermal diffusion This can also be applied if there is a difference in the diffusion energy barrier of (including extrinsic and intrinsic defect levels); for example, the base semiconductor may be Si, Ge, etc.
, InP, GaAs, AIGaN, AlGaP, Al
It does not matter whether it is GaInSb, Zn5e, C (diamond), etc., and whether it is crystalline or amorphous.

In addition, the impurity atoms can be not only ordinary donor and acceptor elements but also, for example, reduction metal elements, and the type thereof is not limited.

〔Effect of the invention〕

In this way, the Li dose Z produced by the method of the present invention
It can be seen from the electrical characteristics of nS that p-type ZnS, which could not be achieved by conventional methods, can be produced. In this way, the present invention enables the position of impurity substitution into a semiconductor to be controlled by an electric field and thermal diffusion, and is expected to be utilized for doping impurities into all semiconductors.

[Brief explanation of the drawing]

1 and 2 are principle diagrams shown in the order of steps to explain one embodiment of the present invention.
high temperature thermal diffusion step (step 1). Figure 2 shows the electric field and thermal diffusion process (process 2) of Li into ZnS.
) is shown. 1...ZnS bulk crystal, 2...quartz ampoule, 3
... ZnS powder, 4... Electric furnace, 5.6... Heater, 7... Quartz ampoule, 8.9... Tungsten electrode, 10... ZnS bulk crystal, 11... Z
nS powder, 12.13...Platinum wire, 14.15...
Through electrode, 16... Power supply, 17... Electric furnace, 18.
19... Heat up.

Claims (1)

[Claims] Step 1 of introducing an impurity into a semiconductor material; Subsequently, Step 2 of simultaneously applying heat and an electric field to the semiconductor material to replace the introduced impurity only at a desired lattice position; and replacing the introduced impurity at a desired lattice position. 3. A method for doping impurities into a semiconductor material, the method comprising the step of removing impurities that are not present.