Hole transport and doping states in epitaxial Culn1-xGaxSe2

Temperature dependent mobility, resistivity, and carrier concentration measurements were made on epitaxial single crystal thin films of group III-rich CuIn1-xGaxSe2 (CIGS). The films were produced using a hybrid sputtering and evaporation process on GaAs substrates. Samples with average Ga/(In+Ga) values between 0.03 and 1.0 and Cu/(In+Ga) between 0.73 and 1.00 were measured. All films were p type with room-temperature carrier concentrations between 4x10(16) and 2x10(19) cm(-3). Fits to electrical measurements were consistent with the presence of two acceptor levels, with activation energies of 167+/-20 and 42+/-8 meV at low Ga contents, and compensating donors in all samples. Increasing Ga content was found to increase acceptor density and decrease acceptor level depth. Hole mobilities near room temperature were found to be between 167 and 311 cm(2)/V s and peak mobilities were between 439 and 1760 cm(2)/V s. Mobility behavior did not change significantly as a function of composition or the presence of a Ga gradient. (C) 1998 American Institute of Physics. [S0021-8979(98)00403-4].