OPTICAL AND ELECTRICAL-PROPERTIES OF CDGEAS2

Large-grained ingots of CdGeAs2 have been grown from near-stoichiometric melts. Resistivity and Hall coefficient (RH) measurements were made on a large number of samples at 77 and 300 K and in some cases up to 450 K. Good fits to the log RH vs 1/T plots are obtained by using a model that assumes three kinds of electronic levels within the energy gap: donors, shallow acceptors, and acceptors with an ionization energy of 0. 30 eV. The deep acceptors are probably native defects, since their concentration varies by nearly four orders of magnitude from ingot to ingot with little change in impurity concentration. Between the intrinsic absorption edge at about 2. 5 Μm and the two-phonon absorption band at 18 Μm, the optical absorption increases with increasing deep acceptor concentration. By using oriented single-crystal samples ∼ 1 cm on a side, conversion efficiencies as high as 27% have been achieved for second-harmonic generation with single-mode pulses from a CO2 TEA laser. © 1978 AIME.