Electrical characteristics of n-InSb crystals used for sub-mm wave emission and detection
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A detailed study of the electrical characteristics of high purity n-InSb has been under taken. The main aim was to determine the effect of the electrical characteristics on the emission and detection properties of n-InSb. Several samples of high purity n-InSb, with different electrical properties, were used. Calculations of the individual and combined effects of the relaxation and excitation mechanisms on the samples were made. Lattice temperatures of 1.5, 4.2 & 77 Kelvins were considered. The electrical properties predicted, agree well with previous results. The variation of current density with electric field was measured at lattice temperatures of 1.5 & 4.2 K, from which the conductivity was calculated. The carrier concentrations of the crystals were measured and the mobilities were then calculated. At an electric field of 0.25 Vcm-1, a sharp rise in conductivity was observed in all samples and attributed to a transition between energy relaxation mechanisms. At an electric field of 20 Vcm-1, one sample showed a sharp rise in conductivity, which was shown (by Hall measurements) to be due to the ionisation of deep donors. At an electric field of 80 Vcm-1, a large increase in conductivity with an associated hysteresis was observed. Reasons for both are suggested. The hysteresis was also observed in the variation of the crystal resistance with lattice temperature. The implications of this work on the possibilities for a tuneable sub-mm wave source or laser has been discussed.
Thesis, PhD Doctor of Philosophy
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