Laser-beam-induced-current measurements have been used to characterize the extent of reactive ion etching (RIE) induced type conversion in vacancy-dopedp-type Hg0.69Cd0.31Te. The technique allows the spatial extent of RIE induced type conversion to be determined and the donor level concentration profile within then-type converted region to be estimated. For the RIE processing conditions used (410 mT, CH4/H2, 0.4 W/cm2)and an etch depth of 0.2&mgr;m,n-type conversion extending∼1.5&mgr;m into the semiconductor was observed. The simple and powerful approach developed in this work is of general application to the study of semiconductor junctions, and can be applied to a range of processing techniques used in the formation ofp-njunctions in HgCdTe (e.g., epitaxially grown heterojunctions, ion implantation, ion milling and Hg in-diffusion). ©1997 American Institute of Physics.