RF/microwave non-destructive measurements of electrical properties of semiconductor wafers for thermophotovoltaic applications.

摘要

A radio-frequency/microwave measurement system has been designed for non- contacting determination of sheet resistance and excess carrier lifetime of low- bandgap materials and junctions, specifically GaSb-based alloys for thermophotovoltaic (TPV) applications. The design incorporates RF circuitry in the 100--500 MHz frequency range and utilizes a Q-switched YAG laser at 1.32 microns to photo-generate electron-hole pairs and conductivity modulate the material and/or junction under test. Supplementary measurements with a GaAs pulsed diode laser at 904 nm provides a faster transient response with near- surface photogeneration. Initial measurements on GaSb substrates, Zn-diffused materials and epitaxially grown layers are presented and discussed.