Evaporated thin-film CdSe/Se heterojunction diodes

Thin-film vacuum evaporated diodes have been fabricated which exhibit excellent rectification properties, including: (a) 70 volts reverse breakdown, (b) greater than 10⁶rectification ratio over a range of 6 to 30 volts, and (c) 0.5 volt forward offset voltage. The diodes have a "sandwich cell" structure, and the rectification action occurs at a p-n heterojunction formed by a n-type CdSe layer deposited over a p-type Se layer. All of the evaporations are made on unheated substrates, with the Se being crystallized by post-evaporation heating prior to the deposition, of the CdSe. Arrays of 16 diodes with 100 mil²area each have, been fabricated with 100% yield and essentially identical I-V characteristics. Although this work is still in a preliminary stage, the results thus far indicate that these devices should be suitable for use in thin-film integrated circuits in combination with thin-film resistor and capacitor elements.