JPH0551560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vapor phase growth method for epitaxially growing a semi-insulating - group compound semiconductor.

(Prior Art) Semi-insulating epitaxially grown layers are used as current blocking layers in optical devices, especially buried semiconductor lasers.
It is expected to be used as a buffer layer in high-speed field effect transistors, and as an electrical isolation layer in opto-electronic composite integrated devices, and is being used.

As a method for growing this semi-insulating semiconductor layer, the halide transport vapor phase growth method, in which group elements are transported as a halide gas, has the characteristics of excellent mass productivity and uniformity, as well as selective growth in a region of several μm or less. This method is suitable for forming the above-mentioned current blocking layer and separation layer because it allows buried growth. Hereinafter, a method for forming an Fe-doped semi-insulating GaAs layer will be described using a specific example.

The conventional growth method for semi-insulating -group compound semiconductors has been carried out using a vapor phase growth apparatus as shown in Figure 2 (J.Electrochem.Soc, Vol. 124).
1977, pp. 1635-1640).

In the conventional apparatus shown in FIG. 2, a group raw material metal 312 is placed in a reaction tube 252, and a heating furnace 262 for heating the raw material metal 312 and the substrate 242 is installed to cover the reaction tube 252. A generation chamber 322 in which an impurity element 142 for obtaining a semi-insulating semiconductor is placed is installed separately from the reaction tube 252, and an introduction tube 122 extending from the generation chamber 322 is inserted into the reaction tube 252. A heating furnace 332 that heats the generation chamber 322 is arranged separately from the heating furnace 262.

In the conventional example, a chloride vapor phase growth method in which group elements are supplied as chloride gas is used in the halide transport method, thereby growing an Fe-doped semi-insulating GaAs layer. Group raw material metal 3 placed in reaction tube 252 by heating furnace 262
12 of Ga, and GaAs of substrate 242, respectively.
Heat to 850°C and 670°C. On the other hand, the introduction pipe 12
It becomes an impurity element 142 for obtaining a semi-insulating semiconductor layer in the generation chamber 322 provided on the upstream side of 2.
Fe (iron) is added and heated in a special heating furnace 332,
Temperature control within the range of 370℃~550℃. Generation chamber 3
When HCl is introduced into 22, Fe and HCl react and form a solid.
_FeCl2 is produced. A part of the generated FeCl ₂ becomes FeCl ₂ gas due to the vapor pressure at that temperature, and is led to the reaction tube 252 through the introduction pipe 122. On the other hand, AsCl ₃ is supplied to the supply pipe 112.
AsCl ₃ reacts with Ga312 heated to high temperature,
A GaAs growth gas atmosphere is formed in the reaction tube 25.
Introduced within 2.

In this way, an Fe-doped semi-insulating GaAs layer is grown on the substrate 242. In this example, a resistivity value on the order of 10 ⁵ Ωcm was obtained.

(Problems to be Solved by the Invention) In the conventional vapor phase growth method for semi-insulating - group compound semiconductors, the iron surface is formed using solid _FeCl2.
Once covered with Fe, all of the HCl supplied to the generation chamber 322 will no longer be able to react with Fe, and a portion will be introduced into the reaction tube 252 unreacted. As a result, when attempting to grow a semiconductor, such as InP, which is particularly highly reactive to HCl, a problem arose in that the crystallinity deteriorated.

Furthermore, even if an attempt is made to control the transport amount of FeCl ₂ gas using the vapor pressure of FeCl ₂ determined by the set temperature, the temperature in the generation chamber 322 for each growth will change slightly, resulting in a large change in the transport amount. However, there was a problem that the controllability and reproducibility of the resistivity of the grown semiconductor layer was poor. Furthermore, the conventional method requires a dedicated heating furnace 322 for heating the impurity element, and requires a plurality of devices.

The above problems are related to the method of generating and transporting iron halide gas, and are therefore unrelated to the method of forming the growth atmosphere for - group compound semiconductors. Therefore, these problems are not specific to the chloride vapor phase growth method mentioned in the conventional example, but are problems of the halide transport vapor phase growth method in general.

An object of the present invention is to eliminate the need for a heating furnace 332;
The object of the present invention is to provide a controllable and reproducible vapor phase growth method for growing high quality semi-insulating -group compound semiconductor layers.

(Means for Solving the Problems) The present invention provides a vapor phase growth method in which a raw material gas is supplied into a reaction tube and a semiconductor layer is laminated on a substrate placed in the reaction tube, which includes a plurality of reaction chambers. A reactor is prepared, and in the first reaction chamber of the reaction tube, an impurity element to be added to the semiconductor layer and a group raw material metal containing the impurity element at a saturation concentration or more are arranged downstream of the impurity element in the gas phase. Then, a pure group raw material metal is placed in the second reaction chamber, and a halide gas is caused to react with the impurity element and each group raw material metal by flowing into the first and second reaction chambers, and the raw material gas is placed in the reaction tube. It is characterized by the fact that it supplies

(Function) According to the present invention, by installing an impurity element, a group raw material metal containing the impurity element, and a pure group raw material metal in independent first and second reaction chambers, the impurity gas can be removed. A group raw material gas containing .

The reason why the impurity element and the group raw material metal containing the impurity element at a saturation concentration or higher are arranged downstream of the impurity element in the first reaction chamber are as follows. For example, when Fe is used as the impurity element, a small portion of the supplied halide gas reacts with Fe to generate Fe halide gas. Almost 100% of the halide gas that does not contribute to the reaction reacts with the downstream group raw material metal to generate group halide gas. If there were no group raw material metal, unreacted halide gas that did not react with Fe would reach the substrate and reduce the crystallinity of the growth layer, but by installing a group raw material metal, this problem can be solved. is resolved.

Furthermore, the reason why the group raw material metal in the first reaction chamber contains an impurity element at a saturation concentration or higher is to prevent the flow rate from decreasing due to Fe halide gas generated upstream reacting with the downstream group raw material metal. be. If the group source metal is pure, the Fe halide gas generated upstream will react with the group source metal and be reduced. This reaction proceeds until the amount of Fe dissolved in the group raw material metal is saturated.

Therefore, simply placing a pure group raw material metal containing no impurity elements will result in poor reproducibility of the electrical semi-insulating properties of the grown layer.

The reason for installing the second reaction chamber is that in addition to the impurity gas and group material gas generated in the first reaction chamber,
This is to enable the group raw material gas to be added to the growth gas independently. This makes it possible to freely control the electrical semi-insulating properties of the grown layer.

(Example) FIG. 1 is a schematic diagram of a growth apparatus for growing an Fe-doped semi-insulating semiconductor layer in an example of the present invention. Inside the reaction tube 251 are independent first
It consists of a growth chamber 191 and a second growth chamber 231. The first growth chamber 191 is a chamber for growing a semi-insulating semiconductor layer, and is partitioned into a first reaction chamber 161 and a second reaction chamber 171. In the first reaction chamber 161, Fe is placed as an impurity element 141 for doping to obtain a semi-insulating semiconductor layer, and in the downstream thereof, Fe is placed at 1ωt% as a group raw material metal 151 containing the impurity element 141. In containing is placed. The reason for setting it to 1ωt% is to keep the Fe concentration in In at or above the saturation concentration (approximately 0.5ωt%). In the second reaction chamber 171, pure In is placed as a group raw material metal 181. The second growth chamber 231 is a chamber for growing S-doped n-type InP, and In is placed in the growth chamber 231 as the group source metal 221. The substrate 241 is
It has a mechanism that allows movement between the first and second growth chambers, and a heating furnace 2 for heating the reaction tube 251.
61 is installed to cover the reaction tube 251.

Using this apparatus, growth was performed using a hydride vapor phase growth method in which a group element is supplied as a hydrogenation gas. HCl is used as the hydride gas, and H ₂ gas containing HCl1c.c./min is supplied to the first growth chamber 191 in the supply pipe 111.
H ₂ gas containing 10 c.c./min of HCl was flowed through 31, and H ₂ gas containing 15 c.c./min of PH ₃ was flowed through the inlet pipe 121, respectively. The second growth chamber 231 includes a supply pipe 2
H ₂ gas containing HCl 10 c.c./min in 11, inlet pipe 20
1 contains PH ₃ 15c.c./min and H ₂ as a dopant gas.
H ₂ gas containing S was passed through each. Heating furnace 26
1, the reaction chamber region was set to 830° C., and the growth region where the substrate 241 was placed was set to 600° C., and heated.

Under the above conditions, an Fe-doped semi-insulating InP layer was grown in the first growth chamber 191 using S-doped InP with a carrier concentration of 5×10 ¹⁸ cm ^-3 as the substrate 241. After that, the substrate 241 is moved to the second growth chamber 231, and S-doped n-type InP is formed on the semi-insulating InP layer.
The layers were grown epitaxially in succession.

Epitaxially grown Fe-doped semi-insulating
To measure the resistivity of the InP layer,
Ohmic electrodes were formed using AuGeNi. As a result, the resistivity of the Fe-doped semi-insulating InP layer is 7.4
×10 ⁶ Ωcm, confirming that a high-resistance semiconductor has been realized. Furthermore, when similar experiments were conducted 10 times to confirm reproducibility, the variation in resistivity was as small as ±0.1×10 ⁶ Ωcm. Furthermore, dislocation density was measured for crystallinity evaluation. As a result, it was found that the dislocation density of the semi-insulating InP layer was as low as that of the substrate used, and the crystallinity was also good.

The flow rate of HCl flowing into the supply pipe 111 is 0.01cc/min.
When changing from 2 c.c./min, the resistivity becomes 10 ² Ω.
It was possible to vary the resistance from cm to 10 ⁷ Ωcm with good controllability.

In the above embodiment, the hydride vapor phase growth method was used, but if the gas flowing into the chambers other than the first reaction chamber 111 in which the impurity element 141 is installed is changed from PH ₃ to PCl ₃ , the chloride vapor phase growth method can be used. can also be applied.

In the above example, Fe is used as an impurity element.
was used, and InP was used as the compound semiconductor, but the invention is not limited to these impurity elements or compound semiconductors. The impurity element may be Cr, Co, etc., and the compound semiconductor may be GaAs, GaP, etc.

(Effects of the Invention) As described above, by using the vapor phase growth method of the present invention, it is possible to prevent unreacted halide gas, which is transported without reacting with impurity elements such as Fe, from reaching the substrate. Deterioration in quality of the insulating semiconductor layer can be prevented. Further, the flow rate of the halide gas containing impurity elements can be controlled and supplied into the reaction tube with good reproducibility, and as a result, electrical semi-insulating growth can be performed with excellent controllability and reproducibility. Furthermore, a dedicated heating furnace for heating impurity elements is also not required.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment according to the present invention,
FIG. 2 is a schematic diagram of a conventional example. 111, 131, 211... supply pipe, 121,
201, and 122...Introduction tube, 141 and 142...Impurity element, 151...Group raw material metal containing impurity element, 161...First reaction tube, 1
71...Second reaction chamber, 181, 221 and 3
12... Group raw material metal, 191... First growth chamber, 231... Second growth chamber, 241 and 24
2...Substrate, 251 and 252...Reaction tube, 2
61, 262 and 332...Heating furnace, 322...
...Generation room.

Claims (1)

[Claims] 1 In a vapor phase growth method in which a raw material gas is supplied into a reaction tube and a semiconductor layer is laminated on a substrate placed in the reaction tube, a reactor containing a plurality of reaction chambers is prepared, and the first In the second reaction chamber, an impurity element to be added to the semiconductor layer and a group raw material metal containing the impurity element at a saturation concentration or more are arranged downstream of the impurity element in the gas phase, and in a second reaction chamber, a pure group raw material metal is placed. at least the step of disposing a halide gas in the first and second reaction chambers to react with the impurity element and each group raw material metal, and supplying the raw material gas into the reaction tube. A method for vapor phase growth of compound semiconductors.