Method of measuring photo-induced voltage at the surface of semiconductor materials
AssigneeGTE Laboratories Incorporated
InventorEmil Kamieniecki
Life of this patent
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Abstract
A method of determining the photo-induced voltage at the surface of a specimen of semiconductor material. A beam of monochromatic light of low intensity and of wavelength shorter than that corresponding to the energy gap of the semiconductor material is directed at the specimen. The light beam is modulated, and the resulting AC photovoltage signal induced at the surface of the specimen is measured. Measurements of surface photovoltage made in this way can be used to determine the surface space-charge capacitance of the specimen of semiconductor material and, therefore, to characterize the properties of the semiconductor material using conventional capacitance analysis.
Claims4
The method of determining the photo-induced voltage at a region of the surface of a specimen of semiconductor material comprising
- directing a beam of monochromatic light at a region of the surface of a specimen of semiconductor material, the wavelength of the monochromatic light being shorter than that corresponding to the energy gap of the semiconductor material;
- modulating the intensity of the beam of monochromatic light at a frequency (f) so that the intensity (.PHI.) of the light impinging on said region of the surface of the specimen varies from a maximum to a minimum;
- and
- measuring the resulting AC voltage signal (.delta.V.sub.s) induced at the region of the surface of the specimen by the modulated light;
- the intensity of the beam of light (.PHI.) and the frequency of modulation (f) being selected such that the AC voltage signal (.delta.V.sub.s) is directly proportional to the intensity of light (.PHI.) and reciprocally proportional to the frequency of modulation (f);
- (.delta.V.sub.s .varies..PHI./f).
Dependencies are inferred from the claim text.