Pressure dependent extrinsic effects in InSb / by Ian Booth. --
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Electrical transport properties of n and p-type InSb in the temperature range 6.2-300K have been studied under pressures up to 15 kbar using Hall measurements. The donor gap in n-InSb is found to increase linearly with pressure, becoming zero at pressures of 8.4 kbar or less. This is responsible for carrier freeze-out under pressure. Unexpected behaviour is observed in the donor gap, as it appears to decrease abruptly at temperatures near 100K as temperature is lowered. This effect has been investigated and two possible theories explaining it are examined. Mobility measurements at low pressure indicate that at temperatures below 40K scattering processes are dominated by ionized and neutral impurity scattering. At pressures high enough to cause carrier freeze-out the mobility decreases rapidly with temperature. High electric field measurements indicate that ionized impurity scattering is the dominant scattering mechanism in this regime.