Measurement of lateral variation of hole diffusion lengths in GaAs

A technique for making rapidly scanned, high spatial resolution minority-carrier diffusion length measurements in direct band-gap semiconductor thin films is described. Using optical excitation of carriers through a semitransparent Schottky barrier, the technique is nondestructive, and at the highest resolution of 1 μm, permits measurements over a 100-μm square area to be made in a matter of minutes. The technique is applied to the investigation of grain boundaries in large- grained polycrystalline n-type GaAs films and is illustrated by measurements over a region containing an electrically active grain boundary. Application of the method for assessment of uniformity of minority-carrier properties of epitaxial layers is feasible