Patent ID: 8300227

Claim:
A method of z-scan photo-reflectance characterization of a semiconductor structure, the method comprising the steps of: (a) illuminating an area of a surface of the semiconductor structure using an amplitude modulated pump laser beam, wherein (i) the pump laser beam comprises at least one wavelength with energy greater than the smallest interband transition energy of a semiconductor material within the semiconductor structure, thereby inducing time periodic changes in electronic charge density within the semiconductor structure such that the electric field profile within the semiconductor structure obtains a time periodic modulation, and (ii) the semiconductor material within the semiconductor structure is subject to a time periodic modulation of interband transition energies; (b) illuminating a portion of said modulated electric field profile of step (a) with a separate probe laser beam, wherein the probe laser beam comprises at least one wavelength (i) nearby an interband transition energy of the semiconductor material within the semiconductor structure, and (ii) suitable for recording the induced changes in semiconductor material optical response which occur nearby to interband transition energies; (c) recording reflected alternating current probe light from the illumination of the semiconductor structure, wherein the alternating current probe light comprises a photo-reflectance signal; (d) performing a series of photo-reflectance measurements of steps (a), (b), and (c), with the semiconductor structure at a multiplicity of positions along the focal length of the probe light column, wherein an aperture is fixtured in the far field of the probe laser beam; (e) using the information collected in steps (a), (b), (c), and (d) to determine a physical property of the semiconductor structure, including at least one of a nonlinear refraction or a nonlinear absorption.