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Sample structures of ErAs:InGaAs materials. Structure A consists of superlattices of ErAs particles with depositions ranging from 0.05–0.4 ML and layer spacings ranging from 5 to 40 nm. Structure B consists of randomly distributed particles codeposited during semiconductor growth. Each sample is grown on a buffer layer of 100 nm InAlAs and 40 nm n-InGaAs ( Si doped). All samples contain an average 0.3 at. % of ErAs.
High-resolution cross-sectional transmission electron micrograph of randomly distributed particles (structure B). The micrograph confirms the formation of nanometer sized particles. The spatial distribution of the particles appears to be essentially random. For clarity, several particles are highlighted with arrows.
Electronic properties of ErAs:InGaAs structures (a) free electron concentration vs ML of ErAs deposition of structure A with ErAs only (circles, solid line), structure A with Si codoping (diamonds, dashed line) and structure B (square) at room temperature; (b) electron mobility of structures A and B at room temperature; (c) in-plane Seebeck coefficient of structures A and B. The dotted curves are calculated using a linear Boltzmann transport equation; (d) , which appears in the thermoelectric figure of merit, of structures A and B.
Temperature dependent Hall data comparing the structure A sample with 0.05 ML deposition and 5 nm spacing (circles) with structure B (squares) over the temperature range 4–400 K; (a) free electron concentration; (b) electron mobility.
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