Pressure sensors based on silicon doped GaAs–AlAs superlattices

Abstract

We show how GaAs–AlAs short period superlattices, in place of AlGaAs thin layers, improve the performances of n-type III–V semiconductors as pressure sensing material. Pressure induced electron capture on relaxed silicon donor sites (so called DX center) is responsible for the high pressure coefficient of resistance (30% per kbar). In comparison to AlGaAs, band gap engineering is employed to optimize both pressure and temperature sensitivities of GaAs–AlAs pseudoalloys between 0 and 200 °C under pressures up to 2000 bars. An electrical characterization is made by performing resistance and Hall effect measurements as functions of hydrostatic pressure and temperature on two microstructures forming the monolithic transducer. The heterostructures consist of (GaAs)9–(AlAs)4 superlattices doped with silicon at concentrations of 1.4×1017 and 2×1018 cm−3, respectively. Accurate pressure measurements (resolution less than 0.2 bar) are performed on two resistors patterned on these microstructures. Monolithic microsensors can be designed on such a stacked GaAs–AlAs two-resistor microstructure.