Silicon microcrystals with high piezoresistance at cryogenic temperatures for sensors application

The studies of piezoresistance of boron doped p-type silicon whiskers with [111] crystallographic orientation mounted on the spring elements, fabricated of the invar alloy, were carried out in the wide ranges of strains ε = ± 1.26 × 10 -3 rel. units and temperatures 4.2–300 K. The measurements were carried out in a helium cryostat. There were investigated silicon whiskers with different types of boron doping: 1) heavily doped crystals with metallic conductivity; 2) in the vicinity of metal-insulator transition (MIT) from the metallic side of MIT and 3) in the vicinity of MIT from the insulating side of MIT. Resistance vs. strain (tensile and compressive) dependences at fixed temperatures: 4.2 K, 77 K and 300 K for Si were measured fo whiskers, mounted on in the tempereture range 4.2-300 K for the heavily doped silicon whiskers in the whole temperature range. The classic piezoresistance was ob-served. Non-classic piezoresistance at helium temperatures was revealed In Si whiskers with definite boron concentration in the vicinity of MIT. Gauge factor of Si whiskers with boron concentration presencefrom the insulating side of MIT achieves at 4.2 K the magnitude GF 4,2 К ≈ –10000 at compressive strain and GF 4,2 К ≥ 8000 at the tensile strain. Obtained characteristics of p-type Si whiskers mounted on the spring elements allowed to forecast the performance of piezoresistive mechanical sensors characteristics on their basis. The possibility of construction of the mechanical parameters sensors (strain gages, pressure sensors etc.) of two types was shown: sensors based on heavily doped p-type Si whiskers for the wide temperature range 4.2–300 K and high-sensitive sensors based on Si crystals with boron concentration in the vicinity of MIT for control and signaling systems at cryogenic temperatures.