KR100359229B1 - Method for Growing n-Type GaAs Monocrystal by Means of VFG - Google Patents

Abstract

The present invention relates to a high-quality n-type GaAs single crystal growth method by the vertical gradient freezing (VGF) method, more specifically doping Si 3 × 10 ¹⁸ cm ^-3 or more etch feed density (EPD) The present invention relates to a high quality n-type GaAs single crystal growth method in which a high quality of etch pit density (≥500 cm ^-2 ) can be ensured by 40% or more.

The present invention applies crystal growth conditions in consideration of thermal balance in order to solve the instability factor of the solid-liquid interface generated when doping Si above (3 to 5) x 10 ¹⁸ cm ^-3. Accordingly, by placing a flat temperature zone from the end of the ampoules so that the heat treatment effect is applied to the ingot, so that the thermal stress after growth is not large, characterized in that consisting of controlling the cooling rate in a single step when cooling to room temperature.

Description

Method for Growing n-Type GaAs Monocrystal by Means of VFG}

The present invention relates to a high-quality n-type GaAs single crystal growth method by the vertical gradient freezing (VGF) method, more specifically doping Si 3 × 10 ¹⁸ cm ^-3 or more etch feed density (EPD) The present invention relates to a high quality n-type GaAs single crystal growth method in which a high quality of etch pit density (≥500 cm ^-2 ) can be ensured by 40% or more.

GaAs materials, which are spotlighted as materials for optical devices, are not universally used like Si, despite their many excellent properties. In the case of n-type GaAs single crystal growth, in order to secure high quality, the Si concentration should be 3 × 10 ¹⁸ cm ^-3 or more. In the case of growth by the conventional HB (Horizontal Bridgeman) method, the temperature gradient is low, This is because constitutional supercooling is caused during growth, making it difficult to obtain a desired single crystal.

That is, the thermal conductivity of GaAs is 3.5 times lower than that of Si and the mechanical properties are also 2 times or less. Therefore, various defects during crystal growth, such as twin or poly-crystal, are easily induced to obtain a desired single crystal. There is a difficult problem.

Therefore, in order to solve the problems of the prior art, the object of the present invention is to dope Si of 3 × 10 ¹⁸ cm ^-3 or more by VGF method to achieve etch pitdensity (EPD: ≧ 500 cm ⁻² ). When the high-quality n-type GaAs single crystal grows with a high quality of 40% or more, the crystal growth conditions are precisely controlled to the microscopic side, so that the optimum growth conditions of the n-type GaAs are applied. An n-type GaAs single crystal growth method is provided.

1A and 1B are schematic cross-sectional views of a furnace before the start of n-type GaAs single crystal growth by VGF method according to the present invention, and a graph showing the relationship between the position and temperature of the furnace during GaAs growth using the same;

2a and 2b are graphs showing a schematic cross-sectional view of the furnace and the relationship between the position and temperature of the furnace at the time of n-type GaAs single crystal growth in accordance with the present invention,

3A and 3B are graphs showing a schematic cross-sectional view of the furnace after n-type GaAs single crystal growth and the relationship between the furnace position and temperature at this time.

(Explanation of symbols for the main parts of the drawing)

1: GaAs melt 2: GaAs seed

3: ampoules 4: sealing

5: end of ampoules 6: GaAs single crystal

7: shoulder portion 8: body portion

G _L : Temperature gradient of liquid part G _S : Temperature gradient of solid part

In order to achieve the above object, the present invention provides crystal growth conditions in consideration of thermal balance in order to solve the instability factor of the solid-liquid interface generated when doping Si to (3 to 5) x 10 ¹⁸ cm ^-3 or more. After the growth, place a flat temperature zone from the end of the ampoules so that the heat treatment effect is applied to the ingot as the growth progresses, so that the thermal stress after growth is not large, and the cooling rate when cooling to room temperature is a simple step according to the temperature. Provided is a high quality n-type GaAs single crystal growth method by the VGF method, which is controlled by the method.

Herein, the crystal growth conditions are variably controlled at a temperature gradient of 5 ° C./cm and a growth rate of 3 to 5 mm / hr, and the flat temperature range is 1080 to 1150 ° C.

The cooling rate is set at 1 ° C / min at temperatures between 1200 and 1000 ° C, 2 ° C / minutes at temperatures between 1000 and 800 ° C, and 10 ° C / minutes at 800 ° C and below.

As described above, in the present invention, by precisely controlling the crystal growth conditions to the microscopic side during the growth of high-quality n-type GaAs single crystals, the optimum growth conditions of the n-type GaAs are applied, thereby providing a relatively homogeneous, high-quality, high-quality n- The type GaAs single crystal can be grown.

(Example)

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, the temperature gradient during growth was set at 5 ° C./cm in the solid part of the solid-liquid interface and 1 ° C./cm or less in the liquid part, thereby facilitating latent heat release during growth. In particular, in this case, considering the thermal balance of the solid portion and the liquid portion, the following Equation 1 is established, and when the arrangement is made according to the growth rate R of the GaAs single crystal 6, the following Equation 2 is obtained.

KsGs = K _L G _L + RLρ

Where R: GaAs single crystal growth rate (cm / hr)

Ks: Thermal Conductivity of GaAs Solids

K _L : Thermal conductivity of GaAs liquid G _S : Temperature gradient of solid part G _L : Temperature gradient of liquid part

L: GaAs coagulation latent heat

ρ: number of moles of GaAs per unit volume

That is, it is necessary to give a growth rate based on the single crystal growth rate R according to Equation 2 in consideration of the thermal balance.

Therefore, the single crystal growth method of the present invention is characterized by the GaAs solid-liquid interface induced during growth when doping Si (3 to 5) x 10 ¹⁸ cm ^-3 for high quality n-type GaAs single crystal (6) growth. In order to artificially control the instability factor, the following three points were applied.

First, growth conditions considering thermal balance were applied.

Second, as the growth progressed, a relatively flat temperature zone was set at 1080 to 1150 ° C. from the end of the ampoules so that the heat treatment effect was applied to the ingot so that the thermal stress was not large after growth. This can be seen by comparing the graphs showing the relationship between the temperature and the position of the furnace before and after growth of FIGS. 2B and 3B.

Third, the cooling rate to room temperature was controlled to ensure reproducibility of high quality.

The present invention considers such a thermal balance as the most important variable in order to ensure high quality reproducibility, as shown in Figure 1, the GaAs melting portion has a temperature range of 1240 ~ 1250 ℃, the ampoules end 5 It becomes 1100-1050 degreeC, and the temperature gradient of the solid part of a solid-liquid interface is set to 5 degrees C / cm between 1230-1240 degreeC, and 1 degrees C / cm or less between 1240 degreeC and 1250 degreeC.

In addition, the growth rate is efficiently controlled at 3 mm / hour for the seed part 2, 5 mm / hour for the show rate part 7, and 4 mm / hr for the ingot body part 8, and the cooling rate is 1200 to 1200. If the Si concentration is doped by (3 to 5) x 10 ¹⁸ cm ^-3 by controlling it to 1 ° C / min up to 1000 ° C, 2 ° C / min up to 1000-800 ° C, and 10 ° C / min below 800 ° C, An n-type ingot is obtained, and operation reproducibility becomes more than 75%.

Example 1

Tested under the above growth and cooling conditions using sides of the <100> orientation to obtain 2 ″ and 2.5 ″ circular wafers, when doped with Si of (1-5) × 10 ¹⁸ cm ⁻³ , 3 × 10 ¹⁸ 500≤EPD≤2000㎝ having an electron concentration of ㎝ ^-3 can be obtained a single-crystal GaAs with a reproducibility of about ^-2.

As described above, in the present invention, by precisely controlling the crystal growth conditions to the microscopic side during the growth of high-quality n-type GaAs single crystals, the optimum growth conditions of the n-type GaAs are applied, thereby providing a relatively homogeneous, high-quality, high-quality n- The type GaAs single crystal can be grown.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (4)

Growth rate (R) of GaAs single crystals in consideration of thermal equilibrium in order to solve the instability of the solid-liquid interface generated when doping Si above (3 to 5) x 10 ¹⁸ cm ^-3 during the growth of GaAs single crystals As shown in Equation 1 below, and put a flat temperature zone from the end of the ampoules so that the heat treatment effect is applied to the ingot as the growth progresses, so that the thermal stress after the growth is not large, cooling rate at room temperature The high quality n-type GaAs single crystal growth method by the VGF method, characterized in that the control step in accordance with the temperature. (Equation 1) Where R: GaAs single crystal growth rate (cm / hr) Ks: Thermal Conductivity of GaAs Solids K _L : Thermal conductivity of GaAs liquid G _L : liquid temperature gradient G _S : Solid part temperature gradient L: GaAs coagulation latent heat ρ: number of moles of GaAs per unit volume The high quality n-type GaAs single crystal growth by VGF method according to claim 1, wherein the solid portion of the solid-liquid interface is controlled at a temperature gradient of 5 ° C./cm and a growth rate of 3 to 5 mm / hr. Way. The high-quality n-type GaAs single crystal growth method according to claim 1, wherein the flat temperature range is 1080 to 1150 캜. The cooling rate of claim 1, wherein the cooling rate is set at 1 ° C / min at a temperature between 1200 and 1000 ° C, 2 ° C / min at a temperature between 1000 and 800 ° C, and 10 ° C / min at 800 ° C or less. A high quality n-type GaAs single crystal growth method by VGF method, characterized in that.