Method and apparatus for determining a material's characteristics by photoreflectance
US5260772A · kind A · utility
Inventors
Key dates
| Filing date | Jul 20, 1989 |
| Grant date | Nov 9, 1993 |
| Priority date | — |
| Expiry date | Jul 20, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/0695
- 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 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. A stepping motor is preferably utilized for varying the light intensity of the monochromatic light. Additionally, the modulation frequency of the modulated beam and/or the wavelength of the monochromatic light can also be varied by the computer. Growth conditions of semi-conductor materials as well as information about trap times can be obtained by analyzing the energy band gaps and determining the dependence of the in-phase photoreflectance signal on the pump modulating frequency, respectively.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.