Surface-Related Optical Anisotropy of GaInP, InP, and GaP

We have studied the optical anisotropy induced by the (0 0 1) surface reconstruction of GaInP, InP, and GaP annealed under various gas environments in an atmospheric-pressure metal-organic chemical vapor deposition system using reflectance difference spectroscopy (RDS). The RD spectra of InP under a PH₃ partial pressure of 10 Torr in a carrier of H₂ between 500°C and 400°C are consistent with a (2 × 1) surface reconstruction. As the temperature of the InP is lowered to 200°C under PH₃, the signature of the RD spectrum changes. If the flow of PH₃ is removed when the InP cools to 300°C, the RD spectrum remains consistent with the (2 × 1) surface reconstruction down to room temperature. When InP is annealed at 400°C in hydrogen, the RD spectrum becomes consistent with a (2 × 4) surface reconstruction. The temperature-dependent RD spectra of GaInP are very similar to those of InP. The RD spectra of GaP reveal that the P-terminated surface of GaP observed at high temperatures is more stable then either InP or GaInP surfaces in the absence of PH₃. The features of these surface-related RD spectra are quickly quenched in air and, under some conditions, nitrogen. This observation is important for studies of bulk-related, ordering-induced optical anisotropy in GaInP.