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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.« less
Inventors:
 [1]
  1. (Denver, CO)
Issue Date:
OSTI Identifier:
870720
Assignee:
Midwest Research Institute (Kansas City, MO) NREL
Patent Number(s):
US 5581346
Contract Number:
AC36-83CH10093
Research Org:
Midwest Research Institute
Country of Publication:
United States
Language:
English
Subject:
characterizing; semiconductor; materials; photovoltaic; device; apparatus; detecting; mapping; defects; surfaces; polycrystalline; material; manner; distinguishes; dislocation; pits; grain; boundaries; laser; wavelength; illuminating; wide; spot; surface; relatively; shorter; narrower; light; integrating; sphere; apertures; capturing; scattered; etched; intermediate; range; specular; reflection; allowing; near; pass; optical; detection; devices; measuring; intensities; respective; center; blocking; aperture; filter; screen; reflected; nondefect; portions; x-y; translation; stage; mounting; signal; processing; computer; equipment; accommodate; raster; recording; displaying; boundary; defect; densities; special; etch; procedure; included; prepares; produce; distinguishable; scattering; patterns; statistical; relevance; reflectance; measurement; piece; obtained; adding; signals; current; induced; measured; sensing; amplifier; moved; optical detection; current induced; translation stage; light scattering; crystalline material; detection device; light scattered; relatively narrow; signal processing; grain boundaries; semiconductor materials; scattered light; semiconductor material; photovoltaic device; material surface; reflected light; shorter wavelength; polycrystalline material; current sensing; grain boundary; measuring intensities; detection devices; integrating sphere; dislocation pits; illuminating light; intermediate range; characterizing semiconductor; light integrating; signal process; near range; etched grain; wide spot; center block; distinguishes dislocation; mapping defects; /356/

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