POLARIZED LUMINESCENCE STUDY OF ORDERED NONLINEAR-OPTICAL MATERIAL ZNGEP2

Polarized photoluminescence (PL) and cathodoluminescence studies have been made as a function of excitation laser wavelength or electron beam energy for the ordered nonlinear optical material ZnGeP2 grown by the Bridgman method. The luminescence signal is seen to be strongly polarized. Furthermore, several PL peaks appear on top of one large broad band, and the dominant peak shifts to a higher energy position as the excitation energy increases. This observation can be explained by the transitions from three conduction bands (GAMMA6, GAMMA7, GAMMA7) to acceptor. level one triplet ground state levels which parody the top three valence subbands (GAMMA6, GAMMA7, GAMMA6). This explanation agrees well with the theoretical energy band diagram of this pseudodirect band-gap material.