NTD Germanium: A Novel Material for Low Temperature Bolometers

Abstract

Six samples of ultra-pure (|N/\-Nrj|<_ lO^cm-^}, single-crystal germanium have been neutron transmutation doped with neutron doses between 7.5 x lO* 6 and 1.88 x 10l 8 cnr 2. After thermal annealing at 400°C for six hours in a pure argon atmosphere, the samples have been characterized with Hall effect and resistivity measurements between 300 and 0.3 K. Our results show that the resistivity in the low temperature, hopping conduction regime can be approximated with P = p 0 exp(A/T). The three more heavily doped samples show values

Metal-insulator transition of isotopically enriched neutron-transmutation-doped70Ge:Gain magnetic fields

“…We use the NTD process since it is known to produce the most homogeneous, perfectly random dopant distribution down to the atomic level. [20][21][22][23] The concentration N of Ga acceptors is determined from the time of irradiation with thermal neutron. The concentration N is proportional to the irradiation time as long as the same irradiation site and the same power of a nuclear reactor are employed.…”

“…This result was obtained from precisely doped samples with a perfectly random distribution of impurities; our 70 Ge:Ga samples were prepared by neutrontransmutation doping (NTD), in which an ideally random distribution of dopants is inherently guaranteed down to the atomic level. [20][21][22][23] For the case of melt-(or metallurgically) doped samples that have been employed in most of the previous studies, [3][4][5][15][16][17][18][19] the spatial fluctuation of N due to dopant striations and segregation can easily be on the order of 1% or more across a typical sample for the four-point resistance measurement (length of ∼5 mm or larger), 24 and hence, it will not be meaningful to discuss physical properties in the critical regime (e.g., |N/N c − 1| < 0.01), unless one evaluates the macroscopic inhomogeneity in the samples and its influence on the results. A homogeneous distribution of impurities is important also for experiments in magnetic fields.…”

Advanced far-infrared detectors

“…In the case of Ge we obtain acceptor and donor dopants in a fixed ratio which is given by the atomic abundance of the individual isotopes and their respective 18 neutron capture cross sections ( 48,49). For natural Ge, which is composed of five stable isotopes, we obtain a Ga acceptor concentration of…”

Ge-Au eutectic bonding of Ge {100} single crystals

“…From the decrease in resistivity, the energy deposited by the incident particle can be determined. 6 . The use of composite bolometers in low temperature applications has created the need for a means of adhering thermistors to the antenna with minimal phonon scattering at the bonded interface.…”