NTD germanium: A novel material for low-temperature bolometers

Six samples of ultra pure (absolute value N/sub A/ - N/sub D/ absolute value cu cm 10 cu cm, single crystal germanium were neutron transmutation doped with neutron doses between 7.5 quadrillion and 1.88 quintillion sq cm. After thermal annealing at 400 C for six hours in a pure argon atmosphere, the samples were characterized with Hall effect and resistivity measurements between 300 and 0.3 K. Results show that the resistivity in the low temperature, hopping conduction regime can be approximated with rho = rho exp (sub o T). The three more heavily doped sampls show values for rho delta and sub o ranging from 430 to 3.3 omega cm and from 4.9 to 2.8 K, respectively. The excellent reproducibility of neutron transmutation doping and the values of rho sub o and delta make NID Ge a prime candidate for the fabrication of low temperature, low noise bolometers.