Low temperature measurements on compensated Germanium with application to Bolometry

Abstract Samples of Ga doped Ge compensated with Sb have been studied over the temperature range 0.38–0.60K. At 0.38K measured and calculated noise equivalent power, NEP, values as low as 5 × 10 −15 W Hz 1 2 and responsivities, R , as high as 10 6 V W were obtained with a thermal conductance, G = 10 −6 W K . It is shown theoretically that some samples could operate below 0.1K with resistances −15 W Hz 1 2 , and R > 5 × 10 6 V W . For these materials the temperature coefficient of resistance, α, has a large effect on the value of R , but little effect on the NEP value. The NEP value is decreased much more by lowering the temperature. It is also shown that the values of R and the NEP are insensitive to the difference between bolometer and bath temperatures, Δ T , over a wide range, and that the low temperature resistance is very sensitive to the dopant concentrations and the degree of compensation.