Enhancement in below bandgap room temperature infrared transmission has been observed in tellurium (Te)-doped GaSb bulk crystals. The effect of Te concentration on the transmission characteristics of GaSb has been experimentally and theoretically analysed. Undoped GaSb is known to exhibit p-type conductivity with residual hole concentration of the order of (1-2) × 10 17 cm −3 at room temperature due to the formation of native defects. For such samples, inter-valence band absorption has been found to be the dominant absorption mechanism. The residual holes could be compensated by n-type dopants such as Te. With increasing Te concentration, free carrier absorption due to electrons and inter-valley transitions in the conduction subband become significant. The dependences of various absorption mechanisms as a function of wavelength have been discussed in this paper.
We report femtosecond optically excited terahertz ͑THz͒ emission from tellurium doped GaSb at room temperature. The influence of the majority and minority carrier type and concentrations on the strength of the THz emission is investigated. Strong enhancement of THz emission in GaSb is observed as a result of compensation of native acceptors by tellurium donors. Surface field acceleration and the photo-Dember effect are identified as THz emission mechanisms in GaSb and modeled in dependence of the majority and minority carrier type and concentrations in our GaSb samples. THz emission from p-type GaSb is dominated by the photo-Dember effect whereas THz emission from n-type GaSb is dominated by surface field acceleration. The doping conditions under which THz emission is maximized are identified.
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