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Title: System for characterizing semiconductor materials and photovoltaic device

Apparatus for detecting and mapping defects in the surfaces of polycrystalline material in a manner that distinguishes dislocation pits from grain boundaries includes a first laser of a first wavelength for illuminating a wide spot on the surface of the material, a second laser of a second relatively shorter wavelength for illuminating a relatively narrower spot on the surface of the material, a light integrating sphere with apertures for capturing light scattered by etched dislocation pits in an intermediate range away from specular reflection while allowing light scattered by etched grain boundaries in a near range from specular reflection to pass through, and optical detection devices for detecting and measuring intensities of the respective intermediate scattered light and near specular scattered light. A center blocking aperture or filter can be used to screen out specular reflected light, which would be reflected by nondefect portions of the polycrystalline material surface. An X-Y translation stage for mounting the polycrystalline material and signal processing and computer equipment accommodate raster mapping, recording, and displaying of respective dislocation and grain boundary defect densities. A special etch procedure is included, which prepares the polycrystalline material surface to produce distinguishable intermediate and near specular light scattering inmore » patterns that have statistical relevance to the dislocation and grain boundary defect densities. A reflectance measurement of the piece of material is obtained by adding together the signals from the optical detection devices. In the case where the piece of material includes a photovoltaic device, the current induced in the device by the illuminating light can be measured with a current sensing amplifier after the light integrating sphere is moved away from the device. 22 figs.« less
Inventors:
Issue Date:
OSTI Identifier:
415731
Assignee:
Midwest Research Inst., Kansas City, MO (United States) PTO; SCA: 360602; 360606; 140501; PA: EDB-97:015423; SN: 97001714622
Patent Number(s):
US 5,581,346/A/
Application Number:
PAN: 8-314,201
Contract Number:
AC36-83CH10093
Resource Relation:
Other Information: PBD: 3 Dec 1996
Research Org:
Midwest Research Institute
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 14 SOLAR ENERGY; SEMICONDUCTOR MATERIALS; DISLOCATIONS; GRAIN BOUNDARIES; PHOTOVOLTAIC CELLS; PHOTOCURRENTS; LASER RADIATION; LIGHT SCATTERING; POLYCRYSTALS