ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Cryogenic bolometric sensors made from epitaxially grown Si:As have been tested down to 40 mK. The sensors were grown by chemical vapour deposition with a doped layer 8.4 µm thick. The dopant concentration was measured using SIMS and was constant, ±1%, with an excellent box profile. Arsenic concentrations up to 7.5 × 1018 cm−3 were achieved. Above 100 mK the low power resistance R(T) followed the variable range hopping law, or Efros-Shklovskii law for a Coulomb gap, R(T) = R 0 exp(T 0/T)1/2 with T 0 ≈ 25 K, typically. A double sensor arrangement was used to measure the electron-phonon coupling in the sensors and the phonon coupling to the heat sink. As the dc current bias through a sensor was increased, spontaneous voltage oscillations were observed across the sensor below 100 mK, which limited the sensitivity of the sensors in this region. These are circuit-limited oscillations between high and low resistance states. A phase diagram was established for the spatio-temporal coexistence of the two states, with a critical temperature T c = 115 mK. We show that this is an intrinsic phase transition within a thermal model of the electron-phonon coupling. For a resistance-temperature characteristic given by the Efros-Shklovskii law we find T c = 0.00512 T 0, independent of R 0 and the coupling strength. This predicts T c = 115 ± 4 mK in this case. The model gives excellent agreement for the critical voltage and current, by assuming that the breakdown occurred via the formation of a filamentary region of high current density and high electron temperature. At higher currents, the response was temperature independent and given by I(E) = I(0) exp{−(E 0/E)1/2} where E is the average applied electric field and E 0 ≈ 380 V/cm, in agreement with a thermal model which includes the phonon-phonon coupling to the heat sink.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s10909-005-0079-z
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