Transmission mappings (500 μm×500 μm resolution) at wavelengths of 0.9–1.5 μm on 3 in., n+‐GaAs wafers (n≂1–2×1018 cm-3) correlate well with carrier concentration n, measured by the Hall effect, and dislocation density, as confirmed by KOH etch‐pit patterns. The absorption for λ≳1.0 μm (below band edge) varies directly with n via free‐carrier interconduction‐band transitions, while the absorption for λ≲0.95 μm (near band edge) varies inversely with n because of band‐filling effects. Both phenomena are highly useful for n+‐GaAs wafer characterization.
Look, D. C.,
Walters, D. C.,
Mier, M. G.,
& Sizelove, J. R.
(1994). Nondestructive Mapping of Carrier Concentration and Dislocation Density in N(+)-Type GaAs. Applied Physics Letters, 65 (17), 2188-2190.