Patent ID: 7659979

Claim:
A method for modulation spectroscopy of a semiconductor sample, the method comprising the steps of: irradiating for an irradiation time at least a location on the sample at a radiation intensity and a radiation wavelength sufficient to cause a change in the sample for at least an enhanced measurement time, halting the irradiation of the sample at the end of the irradiation time, directing an incident probe beam at the location on the sample during the enhanced measurement time to produce a reflected probe beam, directing a modulated pump beam at the location on the sample during the enhanced measurement time, thereby causing a modulation of the reflected probe beam, receiving the reflected probe beam with a detector that generates as output a direct current signal that is proportional to an intensity of the reflected probe beam and an alternating current signal that is proportional to the modulation of the reflected probe beam, and analyzing at least a portion of the output generated during the enhanced measurement time but not during the irradiation time to determine properties of the sample.