Preparation and properties of silicon-cadmium selenide p-n heterojunctions

The vacuum deposition of thin (0.3-0.6 μm) n-CdSe films on p-Si substrates is described, together with an evaluation of the heterojunction properties. Results obtained using both pulsed and steady state light conditions are reported. The devices show in the reverse direction, i.e. with the top electrode biased positively, a low dark conductivity (σ≅1.5 × 10-6 mho cm-2) and a high dark-to-light resistance ratio ( ρ{variant}D ρ{variant}L > 104 at 1.0 V). In this mode of operation, the properties of the heterojunction, rather than those of the photoconductive film, determine the over-all device behavior, as evidenced by the fast rise and decay times (< 3 μsec) and the low values of the photoconductive gain (≅0.25). These and other results can be related to the properties of the constituent semiconductors. © 1972.