SEDL / STP / STP712-EB / STP35141S

Laser Scanning Technique for the Investigation of Power Devices

Engström, O
RIFA AB, Integrated Circuits Division, Spånga,

Drugge, B
ASEA AB, Central Research and Development Department, Västerås,

Tove, PA
Institute of Technology, University of Uppsala, Uppsala,

Pages: 12    Published: Jan 1980

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Abstract

A measurement technique in which inhomogeneities in lifetime or resistivity or both in large-area semiconductor p-n devices can be visualized, is described. The method utilizes a light spot that is scanned across the device area. By using a double-pass method in which the beam is scanned twice for two different bias voltages, the influence of the surface is eliminated. Absolute values of minority carrier diffusion lengths can be obtained by using a red (0.63-μm) and an infrared (1.15-μm) heliumneon laser in combination. Illuminating the specimen with light of 0.63-μm wavelength and measuring the photocurrent as a function of the space charge region width yields the diffusion length for holes in the n region. Using light of 1.15-μm wavelength in the same type of measurement yields the diffusion length of electrons in the p⁺ region.