HOLE TRANSPORT AND DOPING STATES IN EPITAXIAL CULN(1-X)GA(X)SE(2)

Temperature dependent mobility, resistivity, and carrier concentration measurements were made on epitaxial single crystal thin films of grou p III-rich CuIn1-xGaxSe2 (CIGS). The films were produced using a hybri d 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-temperatu re carrier concentrations between 4x10(16) and 2x10(19) cm(-3). Fits t o electrical measurements were consistent with the presence of two acc eptor levels, with activation energies of 167+/-20 and 42+/-8 meV at l ow Ga contents, and compensating donors in all samples. Increasing Ga content was found to increase acceptor density and decrease acceptor l evel depth. Hole mobilities near room temperature were found to be bet ween 167 and 311 cm(2)/V s and peak mobilities were between 439 and 17 60 cm(2)/V s. Mobility behavior did not change significantly as a func tion of composition or the presence of a Ga gradient. (C) 1998 America n Institute of Physics. [S0021-8979(98)00403-4].