Tunnelling current analysis of GaAs n++-p++-n++ ultrathin barrier structures grown by molecular layerepitaxy

摘要

The tunnelling probability for GaAsnn++-p++-n++ ultrathin barrier (UTB)nstructures is calculated based on the parabolic barrier model by usingnthe WKB approximation. The calculated tunnelling current for the UTBnstructure with a 45Å p++ layer grown by molecular layer epitaxy isnin good agreement with the experimental data at room temperature andn77K. This indicates that the MLE-grown epitaxial layers have sufficientncrystal quality and such parameters as doping concentrations and layernthickness are well controlled. The effective tunnelling width at zeronbias is about 97A, which is much smaller than the measured depletionnwidth 190A by the C-V method. The depletion width by the C-V methodncannot be used to estimate the tunnelling current in UTB devices. Thenresults obtained may be applied to the design of ballistic tunnellingndevices