ZnGeP2: A Wide Bandgap Chalcopyrite Structure Semiconductor for Nonlinear Optical Applications

Abstract

ABSTRACTIn this paper we report the growth and characterization of wide bandgap chalcopyrite structure semiconductor ZnGeP2 epitaxial layers by open tube MOCVD and ZnGeP2 single crystals by high-pressure vapor transport (HPVT). The electrical and optical properties of these crystals have been investigated by Hall measurements, absorption spectroscopy, photoconductivity and photoluminescence spectroscopy. The onset of the absorption edge for HPVT ZnGeP2 at 1.99 eV is in accord with the pseudodirect bandgap of this material. Both the meltgrown crystals and epitaxial layers show extended band tailing in the transparency range of ZnGeP2 depending on the growth conditions. Recently we have shown that epitaxial ZnGeP2 films can be grown with excellent surface morphology by MOCVD on (111) GaP substrates. These films should be suitable for phase matched second harmonic generation utilizing CO laser radiation in thick film heterostructures.