Simultaneous Determination of Surface Potential and Excess Carrier Concentration with the Pulsed Surface Photovoltage Method

The surface photovoltage method SPV is by now successfully used for the determination of the energy distribution of surface states [I] as well as of the diffusion length of minority carriers in semiconductor wafers [2, 31. In the first case the equilibrium value of the surface potential yo has to be known in advance which up to now can be suitably ascertained from SPV signals for large light intensities only. However, for some applications concerning, for instance, the spectral response only a moderate light intensity is available. For this reason a new method fur yo determination using SPV signals by employing successively two known intensities of a light pulse is developed and verified with pulsed SPV measurements on high resistivity n type silicon surfaces. The results obtained are confirmed additionally by numerical solutions of the dynamic semiconductor basic equations