Temperature dependence of polarized absorption bands in p-type CdGeAs2 -: art. no. 023105

The temperature and polarization behaviors of four absorption bands in p-type CdGeAs2 bulk crystals have been studied from 5 to 300 K. One band, peaking near 0.22 eV (5.5 mum), is the V-2-->V-1 intervalence band transition, and its intensity taken with Eparallel toc is about 2.8 times larger than that taken with Eperpendicular toc. Three additional absorption bands can be separately resolved below 200 K. A broad band peaking near 0.38 eV is present only with Eparallel toc. A second broad band peaking near 0.52 eV is detected using Eperpendicular toc. These two bands are assigned to transitions from the top two valence bands to a deep acceptor. Infrared photoluminescence studies of a 0.35 eV emission confirm the presence of the deep acceptor. A third absorption band peaking near 0.56 eV is detected using Eparallel toc. This band is assigned to transitions from a shallow 120 meV acceptor to shallow donor states and/or conduction band states. At room temperature, the normally observed broad absorption feature extending from the band edge to beyond 0.2 eV is a result of the superposition of the four bands. These absorption bands presently limit the use of p-type CdGeAs2 crystals as nonlinear optical materials in infrared high-power laser systems. (C) 2005 American Institute of Physics.