Todd R Marshall

US Patent:

57574740, May 26, 1998

Filed:

Jun 28, 1995

Appl. No.:

8/496061

Inventors:

Bhushan L. Sopori - Denver CO
Larry C. Allen - Arvada CO
Craig Marshall - Littleton CO
Robert C. Murphy - Golden CO
Todd Marshall - Littleton CO

Assignee:

Midwest Research Institute - Kansas City MO

International Classification:

G01N 2188

US Classification:

356 72

Abstract:

A method and apparatus for measuring characteristics of a piece of material, typically semiconductor materials including photovoltaic devices. The characteristics may include dislocation defect density, grain boundaries, reflectance, external LBIC, internal LBIC, and minority carrier diffusion length. The apparatus includes a light source, an integrating sphere, and a detector communicating with a computer. The measurement or calculation of the characteristics is calibrated to provide accurate, absolute values. The calibration is performed by substituting a standard sample for the piece of material, the sample having a known quantity of one or more of the relevant characteristics. The quantity measured by the system of the relevant characteristic is compared to the known quantity and a calibration constant is created thereby.