Photoreflectance method and apparatus utilizing acousto-optic mo

Details Photoreflectance method and apparatus utilizing acousto-optic mo Photoreflectance method and apparatus utilizing acousto-optic mo

1989-09-13

1993-10-19

Willis, Davis L.

Optics: measuring and testing

By shade or color

With color transmitting filter

356432, G01N 2125

Patent

active

052550710

ABSTRACT:
A method and apparatus for determining the characteristics of materials, particularly of semi-conductors, semi-conductor heterostructures and semi-conductor interfaces by the use of photoreflectance, in which monochromatic light and an acousto-optically modulated light beam reflected from the sample is detected to produce a d.c. signal and an a.c. signal, whereby the d.c. signal is applied to one input of a computer and the a.c. signal is used with another input of the computer which controls the light intensity of the monochromatic light impinging on the sample to maintain the d.c. signal substantially constant. The modulation frequency of the modulated pump beam and/or the wavelength of the monochromatic light can also be varied by the computer. Information about trap times can be obtained by determining the dependence of the in-phase signal on the pump modulating frequency, respectively.

REFERENCES:
patent: 4589783 (1986-05-01), Thomas et al.
patent: 4632549 (1986-12-01), Czabaffy et al.
patent: 4765742 (1988-09-01), Davinson
Shen et al, "New Normalization Procedure for Modulation Spectroscopy," Rev. Sci. Instrum. vol. 58, #8, Aug. 1987, pp. 1429-1432.
Ginley et al, Photoelectrochemistry and Electrosynthesis on Semiconductor Materials, vol. 88-14 pp. 468-476 Jun. 3, 1988.

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