Photodetection by light-induced barrier modulation in Cu-diffused Au-CdS diodes

Modified Schottky barriers of the type Au-CdS:Cu were prepared by diffusing Cu to a depth of 0.1 to 0.2 µm into single crystals of CdS, prior to evaporating rectifying Au contacts. Modulation of essentially thermionic forward current by light-induced lowering of an electrostatic barrier leads to steady-state electron-per-photon gains in excess of 10⁶at light intensities lower than photons cm^-2sec^-1where response times exceed 1 sec. Barrier-height determinations, in the dark and under illumination with 5000-Å light, by means of internal photoemission, thermal activation energy, and J-V measurements, show unequivocally that under saturating light conditions the potential barrier is reduced by 0.23 ± 0.03 V.