Electron cloud effect on current injection across a Schottky contact

The electron cloud that is formed in the narrow gap material in a modulation-doped heterostructure affects the Schottky contact made to the wide gap material. It also influences absorption and collection of the optically generated carriers. Photocurrent spectra, current-voltage, and current-temperature measurements show that the increase in electron cloud density decreases dark current flow while increasing photoresponsivity. We propose that the Coulombic interaction between the confined electron cloud and the emitted electrons from metal to the wide gap material increases the barrier height. The electric field in the direction of growth due to modulation doping accounts for the increase in photoelectron collection efficiency. Implementation of this effect increases efficiency of photodetectors while, simultaneously, reducing the noise due to dark current. (C) 2000 American Institute of Physics. [S0003-6951(00)00952-9].