The temperature and pressure dependence of the electron and hole mobilities in GaxIn1-xAsyP1-y alloys

Abstract

A wide range of samples of both n-type and p-type GaxIn1-xAsyP1-y on InP has been grown by LPE with carrier concentrations in the low 1016cm−3range. The electron mobility (μe) at room temperature decreased from about 4000 cm2V−1s−1 at y = 0 and passed through a shallow minimum near y = 0.25. At high y values, μe rose steeply, reaching 11 000 cm2V−1s−1 at the ternary boundary. In the p-type material the hole mobility (μp) varied from 140 cm V−1s−1 in InP, passed through a minimum of about 70 cm2V−1s−1 near y = 0.5 and then increased swiftly towards the ternary boundary. The temperature dependence of both μe and μp suggested the presence of alloy or space-charge scattering. In order to distinguish between these two mechanisms the pressure coefficient of the direct band-gap dEo/dP was measured as a function of y by observing the movement with pressure of the photoconductive edge. From dEo/dP the pressure variation of the effective mass was deduced. By measuring the change in electron and hole mobilities with pressure, it was then possible to establish that alloy scattering rather than space-charge scattering was occurring. From the composition dependence of the alloy scattering potentials for electrons and holes predictions have been made of the variation of μe and μP with temperature, pressure and dopant Presently a Nuffield Science Fellow concentration. At room temperature a maximum electron mobility of about 11,200 cm2V−1 s−1 is indicated.