Iron (Fe) concentration dependence of photoluminescence spectra in InP

Recently, a dramatic decrease of residual impurity concentration was achieved in liquid encapsulated Czochralski (LEC) grown InP. In the case of undoped InP, the main residual impurity is Si, which acts as a shallow donor and is incorporated into the InP during the synthesis of polycrystalline InP. Undoped semi-insulating (SI) InP wafers were obtained by high-temperature annealing under high phosphorus (P) over pressure. These undoped LEC InP can now present electric resistivity as high as 1.0 × 10⁷ ohm.cm with mobilities greater than 4000 cm²V^-1s^-1. Iron (Fe) in InP acts as a deep acceptor and is frequently used to obtain a SI InP. Its energy level is located at about 0.78 eV above the top of the InP valence band. The authors present the results of dilute Fe doping into the high quality InP during LEC growth. They focus on the low temperature photoluminescence properties as a function of Fe concentration