J. Lagowski et al., METHOD FOR THE MEASUREMENT OF LONG MINORITY-CARRIER DIFFUSION LENGTHSEXCEEDING WAFER THICKNESS, Applied physics letters, 63(21), 1993, pp. 2902-2904
A procedure is presented for determining long minority carrier diffusi
on lengths, L, from the measurement of the surface photovoltage (SPV)
as a function of the light penetration depth. The procedure uses expli
cit SPV formulas adopted for diffusion lengths longer than the light p
enetration depths. Results obtained on high-purity silicon demonstrate
new capability for noncontact wafer-scale measurement of L values in
a mm range, exceeding the wafer thickness by as much as a factor of 2.
5. This factor can be increased by increasing the accuracy of SPV sign
al measurement. The procedure does not have the fundamental limitation
s of previous SPV methods in which the diffusion lengths were limited
to about 70% of the wafer thickness.