High temperature strain sensors based on gallium phosphide whiskers

Abstract

The paper presents a study of tensoresistive characteristics of p-type GaP whiskers with [111] crystallographic orientation coinciding with the direction of the maximal piezoresistive effect for this material. The authors present a newly-developed technology of creating the ohmic contacts to GaP crystals that allows using these crystals at high temperatures (400—600°C). Tensoresistive characteristics of p-type GaP whiskers were studied in the strain range of ±1,2·10–3 rel. un. These studies show that the gauge factor for these crystals at 20°C is rather large. Thus, for p-type GaP crystals with a resistivity of 0.025—0.03 Ω·cm, the gage factor is in the range of 90—95. The study of tensoresistive properties shows that in the temperature range of 20—300°C for p-type GaP crystals with the resistivity of 0,01—0,03 Ω·cm, the gage factor decreases as the temperature rises, but in the temperature range of 300—550°C for this crystals, very slight temperature dependence of the gage factor was observed. In this temperature range, the temperature coefficient of gage factor is no more than –0,03%/°C. In the temperature range of 300—500°C, the value of gage factor is high (40—50). It could be noticed that in the entire investigated temperature range, the strain sensors based on p-type GaP whiskers have the linear resistance vs. strain dependence in the strain range of ±5,0·10–4 rel. un. The developed strain sensors based on p-type GaP whiskers have high mechanical strength at the static and dynamic strain (more than 108 cycles), which makes them operable in dynamic mode.

Keywords

• whiskers
• gallium phosphide
• sensor
• deformation
• temperature