A detailed composition, intensity and temperature dependent photoluminescence (PL) study of CuInSe 2 has been performed to obtain data on defects, directly comparable to the defects in CuGaSe 2 , prepared under the same conditions. Epitaxial films are grown by metal organic vapour phase epitaxy on GaAs. The PL study reveals three shallow defects, which are responsible for the doping behaviour in CuInSe 2 : two acceptors, 40 and 60 meV deep, and a donor, approximately 12 meV deep. The shallower acceptor dominates for low or no Cu-excess, whereas the deeper one dominates material grown under high Cuexcess. These defects and their compositional dependence are the same as observed in CuGaSe 2 . Thus no fundamental difference concerning the shallow defects exists between these two materials.

Temperature-dependent Hall measurements have been performed on thin films of the ternary chalcopyrite CuGaSe 2 . Unintentionally doped samples and Na-containing samples are compared, as well as epitaxial and polycrystalline ones. Acceptor activation energies and acceptor and donor densities are extracted. Activation energies as well as defect densities vary over a wide range. We demonstrate that all samples are dominated by the same defect with an activation energy of 150 meV in the infinite-dilution limit. It is shown that the degree of compensation increases with increasing acceptor density. Thus direct evidence of self-compensation by intrinsic defects is given. CuGaSe 2 containing Na shows the same defects as CuGaSe 2 without Na: thus, it can be excluded that the dominant effect of Na is the introduction of a new acceptor. In addition, reduced compensation due to Na is not found; the net doping increases in spite of an increased compensation.

No abstract

No abstract

No abstract