EVIDENCE FROM ELECTRICAL-TRANSPORT AND PHOTOLUMINESCENCE SPECTROSCOPY OF A BAND OF LOCALIZED DEEP DONORS IN HIGH-PURITY N-TYPE INP GROWN BY CHEMICAL-BEAM EPITAXY

We have measured the Hall mobility and Hall electronic concentration as a function of temperature of three low-compensation n-type InP epilayers of similar thickness grown by chemical-beam epitaxy. The Hall mobility of the samples was found to be exceptionally high at 77 K and significantly depressed at 300 K. Above the freeze-out region, strong Hall electronic excitation was consistently observed in the temperature range of 35-300 K. These features are in excellent agreement with a model accounting for a broad band of localized deep-donor centers or complexes of unknown origin, centered at 160 meV below the conduction band. In addition, all samples showed an anomalous metal-like behavior at the lowest temperatures, instead of the expected strong localization regime. A broad luminescent band of 11-meV linewidth linked to the presence of the band of deep donors was observed below the acceptor bound-exciton transition. Time-resolved photoluminescence and photoluminescence-excitation measurements supported the bound-exciton nature of the luminescent band. © 1994 The American Physical Society.