Miniature resistance thermometers based on Ge/GaAs films for use in the 1.5 to 300 K, 70 to 400 K, and 200 to 500 K temperature ranges

Resistance thermometers based on Ge films on GaAs substrates have been developed, manufactured, and studied. The thermometers have a miniature package (diameter 1.2 mm and thickness 0.9 mm) and are designed to operate in various temperature ranges from 1.5 to 300 K, 70 to 400 K, and 200 to 500 K. The manufacturing technology, design, low-temperature conductivity, and behavior of the thermometers in a magnetic field are presented. At low temperatures, the conduction of thermometers is variable-range hopping (VRH) with exponents x of 0.25 and 0.45 for different models. Low-temperature transverse magnetoresistance can be positive or negative depending on the manufacturing conditions of the Ge films. Positive magnetoresistance is large and observed in the presence of VRH conductance with an exponent of 0.25, while negative magnetoresistance can be observed in VRH conductance with an exponent of 0.45 and a magnetic field of 0‒3 T. Thermometers designed to operate at high temperatures exhibit two-dimensional percolate transport. The temperature dependence of resistance is described by an exponential dependence with activation energy close to Eg/2. Such Ge thermometers can be used up to 500 K.