Electrical and optical properties of CuInSe2 grown by traveling heater method using pure In and Cu-In alloy solvents

The compound semiconductor crystals of CuInSe2 were grown by the traveling heater method using pure In or Cu-40 at% In alloy as the solvents. The EPMA composition mapping was stoichimetric and homogeneous throughout the crystals. By using the pure In and Cu-In alloy solvents, the n- and p-type conductions resulted, respectively. The carrier concentration and mobility were 4x10(22)similar to 1x10(23) m(-3) and 3x10(-2)similar to 9x10(-2) m(2) V-1 s(-1) for the n-type, while in the order of magnitude of 10(21) m(-3) and 10(-3) m(2) V-1 s(-1) for the p-type at 300 K, respectively. The photoluminescence spectra indicated the characteristic features depending upon the solvents. In the case of the n-type, the origins of the emissions were identified as free exciton and V-Se, while those were free exciton, Cu-In and V-Se in the p-type. The emission intensity measurements indicated that the excitonic emission was predominant in the crystals grown by THM and increased from bottom to top end in the crystals, where lattice defects almost remain constant. The results for the crystals grown by THM showed a clear contrast to that obtained from that by the Bridgman method in which the nonradiative recombination centers were predominant. The laser Raman spectra were almost similar among the CuInSe2 bulk crystals grown by THM and the Bridgman method.