Electron subbands and transport properties in inversion layers of InAs and InP.

Abstract

Subband structures and electron transport are systematically investigated in the two-dimensional inversion layers on InAs and InP metal-insulator-semiconductor field-effect transistors. Hybrid quantum oscillations of conductivity under a strong magnetic field reveal that the two-subband conduction state is realized above an electron concentration ${N}_{s}$ of 1.4\ifmmode\times\else\texttimes\fi{}${10}^{12}$ and 3.8\ifmmode\times\else\texttimes\fi{}${10}^{12}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ for InAs (acceptor concentration ${N}_{A}$=1\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$) and InP (${N}_{A}$=1.7\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$), respectively. Field-effect mobility is observed to decrease abruptly at the onset of the two-subband conduction state at low temperatures. This remarkable effect is due to intersubband scattering. Electron mobility in inversion layers on these III-V compounds is also found to be limited mainly by three scattering mechanisms: screened Coulomb scattering due to the charged interface states at low ${N}_{s}$ values, defect scattering due to the out-diffusion of group-V atoms at intermediate ${N}_{s}$ values, and surface roughness scattering at high ${N}_{s}$ values. Additionally, negative magnetoresistance is observed due to the weak localization effect in the two-dimensional systems. Positive magnetoresistance is also observed in InAs, due to the spin-orbit interaction with a large absolute value of an effective g factor. Finally, intersubband scattering is found to give rise to a remarkable effect on the weak localization.