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A new method is described for determining the distribution of resistivity of semiconductor wafers and thin conducting films. It uses peripheral electrodes to inject small direct currents into the wafer or film and to measure the resultant potential differences, from which the distribution of resistivity is calculated. The usable area of the wafer is not degraded and, because the wafer is scanned electrically, the method is much faster than conventional methods. Results obtained on silicon wafers and conducting films are presented, which demonstrate the sensitivity and reproducibility of the method.

The interpretation of ohmic behavior in semiinsulating gallium arsenide systems A common observation in the photoinduced transient (PITS) spectra of semi-insulating GaAs is the appearance of a negative peak, which is anomalous in that both electron and hole traps should give rise to positive peaks, In this paper, it is shown that the negative peak can be explained in terms of charge exchange with the GaAs surface and only occurs in material which displays particular types of current-voltage and current-temperature characteristics. The dependence of this peak on the processing effects of surface passivation, etching, and baking and polishing has been investigated and its sensitivity to variations in incident light intensity is demonstrated. A new variation of PITS, namely gated-PITS has been employed. This technique suppresses the negative peak in the spectrum, allowing transients corresponding to emission from EL2 to be detected in particular undoped liquid encapsulated Czochralski GaAs substrates for the first time. 215 J.

Historically GaAlAs alloys grown by molecular-beam epitaxy have high deep level concentrations (>1016 cm−3), low luminescent efficiency with broad peaks, and are difficult to dope controllably below mid 1016 cm−3. We report the effect that the low incident antimony molecule fluxes during growth appear to help reduce the density of deep levels below 1014 cm−3, which then allows reproducible doping control in the low 1015 cm−3 range. Exciton-dominated photoluminescence with half widths ∼4.0 meV are now routinely achieved using this technique. Further evidence for the quality improvement of AlGaAs by heavy atom (Sb) doping comes from high 4 K two-dimensional electron gas mobilities for low sheet electron densities, e.g., 1.3×106 cm2/V s for n=2×1011 cm−2. SIMS profiles of antimony content are presented and estimates of incorporated concentrations are given.