On the applicability of InGaP : Si and AlGaAs : Sn piezoresistive pressuresensors in the 2.5 GPa range

Resistivity and Hall concentration was measured in several InGaP:Si and gra ded-gap AlGaAs:Sn epitaxial layers as a function of temperature from 77 to 350 K and of hydrostatic pressure up to 2.5 GPa. Strong pressure variation of resistivity was found together with weak temperature dependence in both types of samples which makes them good candidates for piezoresistive pressu re sensors. The common origin of these properties seems to be the broad dis tribution of impurity states resonant with the conduction band. In InGaP:Si , the broadening of the impurity states is probably due to alloy splitting while in graded-gap AlGaAs:Sn the composition gradient leads to the smearin g of impurity states with respect to the conduction-band edge. The optimum performance of the sensors can be expected if we combine the two mechanisms , i.e., in graded-gap InGaAlP:Si layers. (C) 1999 Elsevier Science S.A. All rights reserved.