JP3430621B2 - III-V compound semiconductor crystal growth method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a carbon-doped III-V compound semiconductor crystal by a metal organic chemical vapor deposition method. [0002] Metal organic chemical vapor deposition (hereinafter referred to as OMVPE)
Is a method of growing a thin film single crystal on a substrate by thermally decomposing an organometallic compound and a metal hydride in a reaction furnace. This method is used for fabricating a heterojunction device substrate using a compound semiconductor, because it is easy to form an ultrathin multilayer structure and has high mass productivity.
Among heterojunction devices, HBTs (hetero bipolar transistors) are being actively developed because they operate at an ultra-high speed. The structure of the HBT is composed of a collector of n-GaAs, a base of p-GaAs, and an emitter of n-AlGaAs. The higher the hole concentration of the base layer, the higher the characteristics of the HBT. Conventionally, in the OMVPE method, Zn has been used as a p-type dopant. However, since Zn has a large diffusion coefficient, it diffuses from the base region to the emitter region during growth, so that a steep pn junction is obtained. There was a problem that can not be. In the MBE method, 1 × 10 ²⁰ cm ⁻³
It is possible to dope to a high concentration to the extent, and
Be having a small diffusion coefficient is generally used, but OMV
In the PE method, it is difficult to use Be due to safety issues. Further, M has a diffusion coefficient that is five orders of magnitude smaller than Zn.
Although doping of g is being studied, biscyclopentadienyl magnesium (Cp2Mg) and bismethylcyclopentadienyl magnesium (M2Cp2
Mg) is easily adsorbed on a pipe or a reaction tube, so that it is difficult to form a steep doping profile. Therefore, carbon doping has recently been studied. A certain document (K. Saito et al., J. Appl. Phys., Vol. 6
4, No.8, p3975-3979 ”), the gas source MBE method
It has been reported that C doping of the order of 10 ²⁰ cm ⁻³ was performed by using TMGa as a group I element and metal arsenic as a group V raw material, and other literatures (Appl. Phys. Lett., TF Kuech et al.
Vol. 53, No. 14, pp. 1317 to 1319 ”), the growth pressure is 76 To.
It is reported that 10 ¹⁹ cm ^-3 C doping was performed by using TMGa as a group III material and TMAs as a group V material at rr. The present inventors have disclosed in Japanese Patent Application Laid-Open No. 3-235
No. 323, when growing C-doped GaAs by the OMVPE method using TMGa and TMAs as raw materials,
A method of controlling the C doping amount by changing the growth temperature was proposed. For example, as shown in FIG. 6, as the growth temperature is increased from 590 ° C. to 660 ° C., the hole concentration becomes 1
It is reduced from 0 ¹⁹ cm ^-3 to 10 ¹⁷ m ^-3 . This method is not a problem when growing a single epitaxial layer, but when growing multiple layers having different C doping levels, the growth is interrupted between the layers and a long time until the next growth temperature is reached. It was necessary to change over time. [0006] Therefore, in the present invention,
III-V group compound semiconductor crystal growth by metal organic vapor phase epitaxy using group V organic metal raw material, which can solve the above problems and can control the C doping amount without changing the growth temperature. It seeks to provide a way. SUMMARY OF THE INVENTION The present invention provides a method for growing a carbon-doped III-V compound semiconductor crystal using an organometallic compound as a group V material by an organometallic vapor phase epitaxy method. By changing the supply ratio between the group III raw material and the group V raw material (however, V
Except for the range in which the molar fraction ratio of the group raw material gas is 1 or less.
Good. ) , A method of growing a group III-V compound semiconductor crystal characterized by controlling the doping amount of carbon. The group III organometallic raw materials used in the present invention include trimethylgallium (TMGa), triethylgallium (TEGa), and trimethylaluminum (TMGa).
Al), triethyl aluminum (TEAl), trimethyl indium (TMIn), and triethyl indium (TEIn). Examples of the group V organic metal raw material used in the present invention include trimethyl arsenic (TMAs) and triethyl arsenic (TEAs). When GaAs is grown using TMAs and TMGa as raw materials, the growth temperature dependency of C doping is as shown in FIG. The activation energy of doping is different. The present inventors have been diligently studying a method capable of controlling the C doping amount without changing the growth temperature, and have found that the supply ratio (V / III ratio) of the group V material and the group III material in the high-temperature region and the low-temperature region described above. Investigation of the dependence of C doping on ()) revealed that the amount of C doping can be controlled by the V / III ratio. That is, in the high temperature region, as shown in FIG.
It was found that the hole concentration decreased in inverse proportion to the V / III ratio, and in the low temperature region, the hole concentration increased in proportion to the V / III ratio, as shown in FIG. Therefore, the C doping amount (hole concentration) can be controlled by changing the V / III ratio at a constant growth temperature in the high temperature region or the low temperature region. (Embodiment 1) Semi-insulating GaAs with the pressure inside the reaction tube kept at 10 Torr and TMAs previously flowing into the reaction tube.
The substrate is heated to a growth temperature of 640 ° C., and then TMG
a was introduced into the reaction tube, and the growth of C-doped GaAs was started. The flow rate of TMGa was set to 6 ml per minute, and the flow rate of TMAs was changed to 50, 35, and 13 ml to 0.5 μm each.
m. The growth is temporarily suspended between the layers, and TMA is stopped.
After the flow rate of s reached a predetermined value (about 1 minute), the growth was restarted. FIG. 1 shows the C concentration (hole concentration) profile in the depth direction obtained from the SIMS measurement of the grown C-doped GaAs.
As shown in Fig. 7, the C concentration changed in inverse proportion to the flow rate of TMAs, and a uniform profile having a predetermined C concentration was obtained in each layer. (Example 2) The pressure in the reaction tube was set to 10 Torr.
The semi-insulating GaAs substrate was heated to a growth temperature of 600 ° C. with TMA flowing through the reaction tube in advance, and then TMGa was introduced into the reaction tube to start growing C-doped GaAs. The flow rate of TMGa was 6 ml per minute, and TM
The growth rate of As was changed to 50, 35, and 13 ml, and each was grown to 0.5 μm. The growth is temporarily suspended between the layers, and after the flow rate of TMAs reaches a predetermined value (about 1 minute).
Growth has resumed. SIMS of grown C-doped GaAs
As shown in FIG. 2, the C concentration (hole concentration) profile in the depth direction obtained from the measurement changes in proportion to the flow rate of TMAs, and a uniform profile having a predetermined C concentration is obtained in each layer. I was able to. According to the present invention, by adopting the above structure, the C doping amount can be easily controlled without changing the growth temperature, and the growth time can be shortened.
Productivity could be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a case where the flow rate of TMAs is changed in Embodiment 1.
It is the graph which showed the C concentration profile of each layer. FIG. 2 shows the results when the flow rate of TMAs was changed in Example 2.
It is the graph which showed the C concentration profile of each layer. FIG. 3 shows a growth temperature set to 640 ° C. in a high temperature region, and TM
It is the graph which showed the change of C concentration when the supply ratio of As / TMGa was changed. FIG. 4 shows a growth temperature set to 600 ° C. in a low temperature region, and TM
It is the graph which showed the change of C concentration when the supply ratio of As / TMGa was changed. FIG. 5 is a graph showing the growth temperature dependence of the C concentration in the growth of C-doped GaAs.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-262332 (JP, A) JP-A-7-22344 (JP, A) JP-A-3-208890 (JP, A) JP-A-7-208 247196 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/205 C30B 25/16 C30B 29/40 502

Claims (1)

Claims: 1. A method for growing a carbon-doped III-V compound semiconductor crystal using an organometallic compound as a group V material by a metalorganic vapor phase epitaxy method. by changing the supply ratio of the group V raw material (however, III group
Of mole fraction of group V source gas to mole fraction of source gas
Excludes the range where the ratio is 1 or less. A method of growing a group III-V compound semiconductor crystal, characterized by controlling the doping amount of carbon.