Profiling of optically active defects

A new method for profiling of optically active defects is presented. Traps in a depletion region are illuminated with chopped extrinsic light
(h\nu < E_{g})
. The resulting ac photocurrent in the external circuit originates from a small part of the depleted layer. The trap profile is obtained by changing the bias voltage which moves the active traps with respect to the semiconductor surface. The method is illustrated with measurements made on an MOS tunnel device.