The formation of dislocations and corresponding built-in electric fields in molecular beam epitaxy (MBE)-grown HgCdTe can have a major impact on the performance and yield of photodetectors fabricated from this material. This paper investigates the presence of such built-in electric fields arising from dislocation segregation in MBE as-grown HgCdTe, and their subsequent removal via a low-temperature Hg-saturated anneal. The electrical properties and surface morphology of an HgCdTe layer grown on a thin CdTe buffer layer are compared with those of an HgCdTe layer grown directly on the CdZnTe substrate. Laser-beam-induced current (LBIC) imaging is a nondestructive technique capable of mapping built-in electric fields present in a semiconductor material, which, in the present case, has been used to reveal dislocation distributions present in as-grown, unintentionally doped, MBE-grown Hg0.71Cd0.29Te. Two-dimensional scanning LBIC measurements at 160 K allow spatial mapping of electric fields across the HgCdTe wafer. Subsequent isothermal annealing of the wafer in an Hg atmosphere has been found to decrease the magnitude of the built-in electric fields to below the LBIC detection limit. However, of particular note, is that before and after annealing, crosshatch patterns can be seen using Nomarski microscopy, with the crosshatching being predominantly in the [01\documentclass[12pt]{minimal}
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