Nanoscale polysilicon in sensors of physical values at cryogenic temperatures

Abstract

Studies of polysilicon in a wide range of concentrations from 2.4 × 1018 to 1.7 × 1020 in temperature range 1.6–300 K and high magnetic fields up to 14Т were carried out in order to predict the characteristics of a material suitable for the creation of microelectronic sensors of physical values based on SemOI-structures. One of the advantages of SemOI-structures is the ability to receive layers with difference in resistivity in a wide range: several orders of magnitude. As it is determined by studies at low temperatures the transfer of charge carriers in polysilicon occurs due to hopping on localized impurities. There have also been found combined mechanisms of current flow at low temperatures, which, depending on the observation temperature, are evident in the transition from the Mott law to the percolation mechanism of Shklovskii-Efros. Those effects can be used to create elements of sensor technology. Sensors of thermal quantities for cryogenic temperatures were developed with TCR = − 9% × K−1 in the range of 4.2–50 K and mechanical quantities for cryogenic temperatures were developed for ultra-sensitivity with coefficient of gauge-factor K = 15500 in the range of 4.2–50 K. Investigation in wide range of cryogenic temperatures was conducted with the purpose of optimizing the geometry of the sensor membrane (its thickness and surface area) in order to obtain optimal stresses and deformations in the membrane. This process is essential for the sensor to be able to provide a sufficient amount of the output signal while maintaining the strength of the membrane and the sensor structure as a whole.