Electrical properties of InGaP : Si and AlGaAs : Sn epitaxial layers

We measured Hall concentration n and mobility mu in InGaP:Si and AlGaAs:Sn epitaxial layers grown on GaAs as a function of pressure up to 2 GPa and at temperatures from 77 to 350 K. We interpreted our results for InGaP:Si in terms of the broad distribution of impurity states resonant with the conduc tion band. For AlGaAs:Sn the resonant impurity states seem to be sharp but the composition gradient moves them with respect to the Fermi level. The br oad distribution of impurity states leads to small temperature effects on c onductivity while the pressure effects remain strong. These features make I nGaP:Si and graded-gap AlGaAs:Sn very attractive as piezoresistive pressure sensors. Moreover, they do not reveal any metastability in the 77 to 300 K temperature range.