Identification of deep levels in liquid-encapsulation Czochralski-grown Fe- and Zn-doped InP: A proof of the nonexistence of a Fe4+/Fe3+ donor level

Abstract

Deep levels in liquid-encapsulation Czochralski (LEC) grown p-type InP:Fe codoped with Zn have been investigated by means of temperature-dependent Hall-effect (TDH), deep-level transient spectroscopy (DLTS), calorimetric absorption spectroscopy, and electron spin resonance measurements. Although a dominant deep hole trap is revealed both by DLTS and TDH measurements in the vicinity of the valence band edge at EV+0.2 eV, the spectroscopic analysis unambiguously invalidates previous speculations on the existence of a second energy level of the isolated iron impurity in the band gap of InP, i.e., a Fe4+/Fe3+ donor level. From the axial concentration profile and a comparison with a LEC-grown p-type InP crystal doped with Zn only it seems that the trap is not even iron-related in contrast to tentative assignments often found in the literature. Native or Zn-related defects which depend on the particular growth conditions used are assumed to account for this level.