uv Microprobe Technique for Measurement of Minority-Carrier Diffusion Length in GaP p-n Junction Material

The minority-carrier diffusion length on either side of a GaP p-n junction have been determined from measurements of the short-circuit current under uv excitation. The uv lines at 3.41 and 3.53 eV are extracted from an Ar laser and are focused to a spot 10 μ in diameter. The uv spot is scanned along the angle-lapped surface of the junction to obtain the variation of short-circuit current as a function of distance normal to the junction from which the diffusion length is derived. The technique provides a determination of diffusion lengths as short as 0.13 μ with an accuracy of 15%. The technique is straightforward and should be useful in the evaluation of GaP and other semiconductor material containing p-n junctions.