Mapping of the localized interface and surface states of InGaAs lattice matched to Fe-doped InP by infrared spectroscopy

Infrared absorption and photocurrent measurements have been applied to study the photoresponse below the band gap of indium gallium arsenide (In0.53Ga0.47As) grown lattice matched to Fe-doped semi-insulating indium phosphide (InP) substrates by various epitaxial growth techniques, including molecular beam epitaxy, liquid phase epitaxy, and metalorganic chemical vapor deposition. It is found that Fe at the InGaAs/InP interface is responsible for exciton-like and polarization sensitive absorption peaks. Both electron and hole emission into the conduction and valence bands, respectively, were observed, and a deep Fe level was identified 0.37 eV below the conduction band edge of bulk Fe:InGaAs. Lowering of the local crystal symmetry due to the interface electric field is proposed to be the mechanism that describes the dipole-allowed interband absorption of 3d transition metal impurities in narrow band gap III-V compounds like the Fe2+:InGaAs used in this study. The ambiguity in distinguishing InGaAs quantum well intersubband absorption signals from the Fe interband absorption signals is also addressed.