| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
(1) Chloride vapor phase epitaxial growth of CuGaS_2
The source materials wore copper monochloride (CuCI), gallium trichloride (GaCl_3) and sulfur (S). The sources were heated in a horizontal four-zone resistance furnace, and transported by a nitrogen carrier gas and mixed in the growth region. GaAs (100) wafers were used for substrates. The growth procedure was as follows. The source materials and substrate wee set at the respective zone in the growth tube, and the system was purged with the N_2 carrier gas. After that, the carrier gas flow rates were reduced to one tenth of the normal flow rates (I I/min for chlorides and 0.1 I/min for sulter) until all the zones reached the required temperatures. The flow rate reduction during the heating-up period before the beginning of the epitaxial growth was found to be effective to prevent doubly oriented growth. At the en ([of the epitaxial growth, all the furnaces were turned off and the carrier gas flow rates were reduced again to one tenth
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of the normal rates. At the same time, the substrates were moved from the growth zone to a low temperature (<200ﾟC) zone. The flow rate reduction and the substrates removal were effective to prevent polycrystallin materials falling on the grown layer during the cooling period. Typical source temperatures were CuCl=450ﾟC, GaCl_3=70ﾟC and S=160ﾟC. The effective transport rates were 2x1O^<-6> , 3x1O^<-6> and 8xlO^<-7> mol/min, respectively.
(2) Very low pressure epitaxial growth of CuGaS_2
CuGaS_2 films were grown on GaAs (100) substrates by chloride MBE method. Molecular beams of gallium, sulfur and copper monochloride were supplied from Knudsen cells in a growth chamber filled with hydrogen gas with a pressure of 1x10^<-4> Torr. Source temperatures were T_<cucl>=220ﾟC, T_<Ga>=850ﾟC and T_s=55ﾟC. Films grown at 600ﾟC showed a strong X-ray diffraction peak of CaGaS_2 (004) reflection. The lattice parameter c was 10.43A and smaller than that of bulk crystals (10.48A). The difference is due to the difference in thermal expansion coefficient between CuGaS_2 and GaAs. Less
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