JPS62176997A - Method for bringing up hemiinsulating inp single crystal - Google Patents

Abstract

PURPOSE:To obtain hemiinsulating InP single crystal doped with Fe in excellent reproducibility through all parts of crystal by making the following iron concn. in an initial period the specified range which is contained in a melt having the prescribed carrier concn. for synthetic InP single crystal and bringing up single crystal. CONSTITUTION:A device for pulling up single crystal due to a Czochralski process provided with used liquid sealing is set in the inside of an external vessel in the high-pressure inert gas atmosphere. A melt and a sealant B2O3 covering the top surface thereof are housed in a crucible 1. The outside of the crusible 1 is surrounded by a graphite susceptor 2 and evaporation of the melt is inhibited by B2O3 and a heater 3 is provided outside the susceptor. Single crystal C is brought up through the B2O3 layer by pulling up a pulling shaft 4. In the applied melt, iron is added to the melt of the raw material for synthetic InP polycrystal which has 8X10<15>-1X10<16>cm<-3> carrier concn. so that iron concn. in an initial period is regulated to 0.030-0.040wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing semi-insulating InP single crystals, and particularly relates to a method for growing semi-insulating InP single crystals, and particularly relates to semi-insulating F single crystals having a resistivity of 107 Ωm or more.
This invention relates to a method for obtaining an a-doped InP single crystal throughout the crystal with good reproducibility.

BACKGROUND OF THE INVENTION InP compound semiconductors are useful as substrate crystals for semiconductor lasers and light receivers in long wavelength bands, and have recently attracted attention as materials for simple FETs. Recently, optical ICs have been developed that integrate photodiodes, FETs, and semiconductor lasers on -InP substrates.
A semi-insulating crystal must be used as the P substrate to facilitate mk separation of these elements.

A semi-insulating InP single crystal can be created by doping the transition gold side with Fe, Co, etc.

These impurities form deep acceptor levels and exhibit semi-insulating properties by compensating for residual carriers. In particular, Fe-doped InP is viewed as promising. There is great interest in the production of semi-insulating Fe-doped InP single crystals having a resistivity value of 107Ω1 or more.

Prior Art and its Problems Generally, when an F-doped InP single crystal is pulled up using the liquid-sealed Czochralski method, Qin2! w1
If the degree is low, the reproducibility of the amount of doping in the obtained single crystal is poor, and the solidification rate of the single crystal of 101Ω (or more) becomes large, resulting in poor yield.

That is, there is a portion in the upper part of the pulled single crystal that does not have a resistance value of 101QcWI. Conversely, when increasing the iron concentration in the melt,
Although the specific resistance of the single crystal increases and the yield improves, precipitation of iron phosphorus compounds (FsP, FePz, etc.) becomes more likely to occur. Further, if the iron concentration is high, the Fe concentration in the wafer becomes non-uniform when the temperature reaches 700 to 800° C. due to epitaxial growth or ion implantation onto the wafer, resulting in non-uniform electrical properties. In this way, if the amount of F doped into the single crystal is small, the resistivity will be 10
The yield of crystals with a resistance of 1Ω or more will be low, and conversely, if it is too large, disadvantages related to the concentration of simple iron will occur.

Conventionally, F-doped InP single crystals are produced by using undoped InP polycrystals, which are created by pulling InP polycrystalline raw materials once using the liquid-encapsulated Czochralski method (LEC method), as raw materials, and It was created by adding F. and pulling an F.-doped InP single crystal from the melt again by the LEC method. According to one experimental example, the following results have been reported: By adding α022% or more of F into the InP melt, the solidification rate is 9-rJ, and the specific resistance is 101Ω or more at 04 or more. Creating single crystals. However, conditions for producing a single crystal having a resistivity of 101Ω or more with good reproducibility and high yield have not been established.

As such, the conventional technology has the following problems: 1 Since pulling is performed once to prepare the raw material, a total of two pulls are required to obtain the semi-insulating F-doped InP single crystal as the final product. It is necessary to raise the amount by the LEC method, which increases costs and reduces productivity.

2. A technology has been established to obtain a semi-insulating InP single crystal with a resistivity of 107Ω or more reproducibly throughout the entire crystal (throughout the entire length from the top to the bottom of the crystal) without causing alignment related to iF/doping amount. Summary of the invention In order to solve the above problems, the present inventors have conducted repeated studies. As a result, regarding problem 1 above, quite surprisingly, there is no difference in product quality even when single crystals are pulled using low-purity polycrystals with a carrier density of 8 x 101" to I x 10" m-3 as raw materials. It was discovered that

Conventionally, unpulled polycrystals (undoped) were used as raw materials for final pulling because it was ruled by the fixed concept that if the raw materials were not of high purity, residual impurities would appear in the final doped product. be.

As a result of repeated experiments, the present inventors have come to confirm that this is a mistaken idea. Carrier density (2~3)
X 101111M, a single crystal obtained by pulling an InP polycrystal with a pot purity of
i# Yaria Density 8 x 10" ~ I x 10"
The purity of the single crystal obtained by pulling a cm-3 InP polycrystal in the same manner does not change. In other words, single crystals with the same carrier concentration and concentration can be obtained regardless of the weight of the polycrystalline carrier used as the raw material. Therefore, for raw material preparation, LE
There is no need to perform pulling using the C method, and the synthesized InP polycrystal obtained by the horizontal Bridgman method is directly used as Fe-doped I
There is no problem in using it as an nP single crystal raw material. For these reasons, the present invention has a carrier density of 8 x 10'' to 1 x 101
The raw material is synthetic polycrystals of 6 tan.

Regarding the second problem, the conditions for producing an F-doped InP single crystal with an appropriate concentration in which the specific resistance is 101Ω or higher and the Pa doping amount is not too high, using the above raw materials. We conducted repeated experiments to improve this. As a result, it was found that the above object could be achieved by pulling the melt using a melt containing α030 to α040 vt% of F.

Thus, the present invention provides a method for growing a semi-insulating F-doped InP single crystal by the liquid-sealed Czochralski method, in which a synthetic InP polycrystal with a carrier concentration of 8 x 10'' to 1 x 10'' m-3 is grown. was used as a raw material, and the initial iron concentration in the raw material melt was set to Q, 030 to α040 wt%, and F-doped InP
A method for growing a semi-insulating InP single crystal is provided, which is characterized by pulling the single crystal.

FIG. 1 schematically shows a single crystal pulling apparatus using the liquid-filled Czochralski method (I, EC method). The device is placed in an external container under an inert gas surface pressure atmosphere. Crucible 1 is a sealant B that covers the melt and its upper surface! It stores 03. A graphite susceptor 2 surrounds the outside of the crucible 1. B2 os suppresses evaporation of the melt. A heater 3 is set outside the susceptor. By pulling up the pulling shaft 4 while rotating the pulling shaft 4 and the crucible shaft 5, the single crystal C is grown through Ih0sR1. For convenience of explanation, the single crystal is shown in a pulled state.

According to the present invention, the melt has a carrier concentration of 8 x 1013~
Synthesis of I x 1016α Iron was added to the melt of the InP polycrystalline raw material so that the initial iron concentration (LOjO to α040 wt%) was obtained.

゛As mentioned above, in the present invention, the trouble of using a raw material that has been purified once by pulling as in the conventional method is avoided, and a relatively pure synthetic InP polycrystal with a carrier concentration of 8 x 10 cm-3 is used. is used as a raw material.This is based on the experimental result that regardless of the carrier concentration of the raw material polycrystal, that is, the level of purity, the single crystal obtained by pulling it shows the same carrier concentration.

(2~S) InP polycrystal (1) with a purity of X 10"cm-" and 8 X 101 polycrystals with a lower purity
When an undoped single crystal was pulled using the LEC method using a low-purity InP polycrystal (2) of I x 10"6R-3 as a raw material, the carrier temperature of the pulled single crystal was as follows: ( 1) Carrier concentration 2 to 5 X I
If the raw material is polycrystalline polycrystalline QIIIon-", the single crystal will be contaminated and its carrier concentration will be 4 to 4.
6X101scm-3 and null. Also (2)+7) 8
When a relatively low purity polycrystal with a carrier concentration of X 10'' to I
It becomes 10”3.

Therefore, regardless of the carrier concentration of the raw material polycrystal, single crystals with the same carrier concentration can be obtained.

The present invention increases the carrier concentration of InP polycrystalline raw material to 8×101
The reason why it is defined as s~l×1015 m is that this level can be easily realized by a synthesis method such as the horizontal Bridgman method. Use of a compound with a purity lower than this range requires additional operations such as purification treatment, which would defeat the purpose of the present invention. If a material with a purity lower than this range is used as a raw material, the purity will be too poor and will affect the quality of the single crystal.

The next objective of the present invention is to use such an InP polycrystalline raw material to achieve a resistivity of 1070 tan or higher throughout the single crystal with good reproducibility, and to establish conditions that do not cause problems related to surface iron doping. This is a challenge.

The relationship between solidification rate and impurity concentration when pulling a single crystal is expressed by the following formula: C = CoK (1-g)K-" g is g at the top of the produced single crystal as shown in Figure 1. ==Q and at the bottom g=α95
Meanwhile, the value increases from O to α95.

In the case of Fe-doped InP single crystal, the segregation coefficient is 10-
3 to 10-4, and this value is 1 due to experimental variation.
There is a digit width. Since fcK<<1, the relationship between the assimilation rate g and the impurity concentration C is as shown in the second -, and as the assimilation rate increases, the impurity concentration C rapidly increases.

Therefore, when doping Fe into an InP single crystal, the amount of iron doped is insufficient in a small g range, and 107
A resistivity of 100 Ω or more and a portion that does not overlap are likely to appear. It is necessary that the initial Fe doping concentration Ci (C value at g=0) reaches a predetermined doping amount level. Since the Fe' doping concentration increases rapidly in the second half, the final Fe doping concentration Cf (g = α95
C value) must be below an acceptable level, that is, a level at which iron does not cause any adverse effects.

Incidentally, the relationship between the Fe concentration and specific resistance in the InP single crystal is shown in FIG. As can be seen from FIG. 3, a specific resistance of 10 γΩ or more can be obtained when the Fea degree is α2 ppmw or more.

Therefore, if it is possible to set the initial concentration of Fe in the melt that provides Fe-doped self-C such that C1 is reliably above α2ppmw and Cf is below the allowable level, the produced Fe
A resistivity of 10<7>Ω or more is guaranteed throughout the doped InP single crystal from the upper end to the lower end, and the adverse effects of an excessively high iron doping amount do not occur. As a result of repeated experiments using the above raw materials, it was found that it is preferable to add iron to the raw material melt so that the initial iron concentration is 1030 to 0.040 wt%. If it is less than 1050 wt%, it is difficult to obtain a predetermined Fe 2 doping amount in a small g range, and a portion with a specific resistance of less than 10 7 Ω appears, resulting in a decrease in yield. When it exceeds 0.040 wt, the iron doping amount exceeds the permissible level in a large g range, and Fl! P
, FOP! Defects such as precipitation of etc. are less likely to occur.

It is preferable to dissolve Fe 2 using α05IIll + rhinoceros foil, for example, because the dissolution rate is fast and undissolved matter HD is less likely to occur.

Semi-insulating Fe-doped InP grown according to the present invention
is useful in examining the original IC board mentioned at the beginning.

Effect of the invention 1: A semi-insulating InP single crystal with a resistivity of 107Ω or more can be obtained throughout the crystal with good reproducibility.

2- Since the Fe doping level is appropriately suppressed, precipitates such as FePH1FeP are not generated, and when the wafer temperature is raised, the F@ concentration in the wafer is not uniform, and the electrical properties are not uniform. There are no harmful effects such as

5. Carrier concentration 8X1[)'''~I X 10''c
Since a polycrystalline raw material with a purity of "m-" is used, the pulling process for purification can be omitted, which increases productivity, contributes to cost reduction, and further advances the development of optical IC devices.

Example: InP polycrystalline I kg of carrier density 9 x 10"cm-" was used as a raw material, and Fe foil of α05-thickness was 350cm thick.
A single crystal was pulled using the liquid-sealed Czochralski method.

At this time, the #A product obtained is: ■ A region with resistivity of 1070 tan or more is obtained in the range of 0<g<195, and ■ Precipitates such as FeP2 and FeP are also delayed, making it a high-quality product. It belonged to

[Brief explanation of drawings]

Figure 1 is a schematic diagram explaining the Czochralski method for manipulative sealing, Figure 2 is a graph showing the relationship between solidification rate and single crystal impurity concentration, and Figure 5 is the relationship between Fe concentration in the single crystal and specific resistance. Here is a graph showing. 1 Nil acupuncture point 2: Susceptor 3: Heater 4: Pulling axis 5 Nil acupoint axis Figure 2 Figure 3 Fe concentration (ppmw) Procedure Ura Masaru March 1986 240

Claims (1)

[Claims] 1) In the method of growing a semi-insulating Fe-doped InP single crystal by the liquid-sealed Czochralski method, the carrier concentration is 8.
×10^1^5 to 1 × 10^1^6 cm^-^3 synthesized InP polycrystals are used as raw materials, and the initial iron concentration in the raw material melt is set to 0.030 to 0.040 wt% to produce Fe-doped InP.
A method for growing a semi-insulating InP single crystal, characterized by pulling a single crystal.