Direct measurement of minority carriers diffusion length using Kelvin probe force microscopy

We report on the use of Kelvin force microscopy as a method for measuring v ery short minority carrier diffusion length in semiconductors. The method i s based on measuring the surface photovoltage between the tip of an atomic force microscope and the surface of an illuminated semiconductor junction. The photogenerated carriers diffuse to the junction, and change the contact potential difference between the tip and the sample as a function of the d istance from the junction edge. The diffusion length L is then obtained by fitting the measured contact potential difference using the minority carrie r continuity equation. The method is applied to measurements of electron di ffusion lengths in GaP epilayers. (C) 1999 American Institute of Physics. [ S0003-6951(99)03742-0].