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Various optical and electrical properties of the I-III-VI2 compounds CuGaS2 and CuInS2 have been studied. From the results of low-temperature luminescence and ref lectivity, both crystals are determined to have a direct band gap. The band gaps at 2'K are 2. 53 eV for CuGa82 and 1.55 eV for CuIn82. CuInS2 has been made conducting both n and. p type, vrhile CuGa82 has been made p type only. Electroreflectance measurements have been performed in an attempt to determine the band structure. The highest valence band appears to be a doublet rvith a 1Rrge admixture of Cu 3d %'Rve functions.

We report CuInSe2/CdS p-n heterojunction photovoltaic detectors which display uniform quantum efficiencies of up to ∼70% between 0.55 and 1.25 μ. Response times as short as 5 nsec have been observed. A weak electroluminescence (0.01% external quantum efficiency) peaking near 1.4 μ has also been observed at room temperature.

The room-temperature electrical properties of ten I-III-VI2 (I=Cu, Ag; III=Al, Ga, In; VI=S, Se) compounds are presented. The resistivities of eight of these compounds are rapidly changed by annealing under maximum and minimum chalcogen pressures. The Cu compounds can readily be made p type, a feature lacking in the analogous II-VI compounds. However, the Cu compounds with energy gaps of 1.7 eV or above have not been made n type.

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