ELECTRODEPOSITED CDTE - OPTICAL-PROPERTIES

For the measurement of optical constants, the electrodeposited films o f CdTe were lifted off their opaque substrates and transferred onto gl ass slides using a transparent liquid adhesive. This technique proved to give results more reliable than those obtained on samples in which CdTe is deposited on CdS-coated conducting glass. The measured optical dispersion in the photon energy range of E<1.5 eV is in excellent agr eement with that for the single crystal. The optical absorption coeffi cient was determined in the E<3.5 eV range and was compared with that for the single crystal. The results revealed two direct allowed transi tions at 1.50 eV [Gamma(8) valence band(VB)-->Gamma(6) conduction band (CB)] and 2.43 eV [Gamma(7)(VB)-->Gamma(6)(CB)] and three indirect all owed transitions at 1.27 eV [L-4,L-5(VB)-->Gamma(d)], 1.83 eV [L-6(VB) -->Gamma(d)], and 2.84 eV [Gamma(8)(VB)-->L-6(CB)]. The 1.27 and the 1 .83 eV transitions, which have not been reported previously and were n ot detected in single-crystal data, are attributed to the transitions to grain-boundary-related defect energy band Gamma(d), 0.65 eV above G amma(8) (VB). The indirect transitions at 1.83 and 2.84 eV are assiste d by phonons having energies of 80 and 84 meV, respectively. (C) 1997 American Institute of Physics.