Sharp Drop in the Mobility of Holes with a Decrease in Their Two-Dimensional Concentration by an External Voltage in Boron δ-Doped Diamond Layers

Abstract

It is shown, both analytically and numerically, that the hole mobility in boron δ-doped (i.e., with a thickness on the order of several lattice constants) diamond layers drops with a decrease in their two-dimensional concentration during depletion of the δ-doped layer by an external voltage. This drop is most pronounced for the maximum initial two-dimensional hole concentrations ~ 3 × 10¹³ cm^–2 (limited from above by the condition for the possibility of their significant reduction without the electrical breakdown of diamond). This is explained by a decrease in the degree of screening of scattering Coulomb potentials of ionized boron atoms and an increase in the scattering efficiency of degenerate holes from these atoms due to a drop in the kinetic energy of holes. The corresponding calculations of the transport scattering cross section of holes are performed beyond the Born approximation (i.e., perturbation theory), which is inapplicable for boron δ-doped diamond layers. The predicted effect can be used to increase the efficiency of source-to-drain current modulation by a gate voltage in diamond field-effect transistors (FETs) with δ-doped conduction channels.