Heat Capacity of Neutron Transmutation Doped Ge Type 18
We present measurements of the heat capacity of neutron transmutation doped (NTD) Ge temperature sensors from 100–300 mK. The NTD Ge sensor studied consists of a 30μm×100μm×250μm block of NTD Ge type 18 with the natural isotopic abundance, a doping of n = 5.6×10^(16) cm^(−3) and ion implanted and metallized contact pads. Each sensor was mounted on a freestanding silicon nitride (Si‐N) pad supported by Si‐N legs each with a cross section in the range 5–10 μm^2. Two of the Si‐N legs were metallized for electrical readout of the NTD Ge sensor. The measured heat capacity of the NTD Ge sensor, which includes the metalization and Si‐N pad, when fit to power law C = C_0T^γ yields C_0 = 4.3pJ/K^γ and γ = 1.6. The thermal conductance, GSi‐N, of the Si‐N support legs was measured over a larger temperature range 80–800 mK. We find G_(si‐N) at temperatures >200 mK of all 4 samples is at or below the 1D or quantum of thermal conductance limit.
Additional Information© 2009 American Institute of Physics. Published online 16 December 2009. We acknowledge the help of Mihhee Yun for fabricating the samples and George Sirbi for mounting them in the copper carrier. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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