Photoreflectance method and apparatus utilizing acousto-optic modulation
US5255071A · kind A · utility
Inventors
Key dates
| Filing date | Sep 13, 1989 |
| Grant date | Oct 19, 1993 |
| Priority date | — |
| Expiry date | Sep 13, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/126
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.