Improved stability in PbS/Al2O3 thin-film transistors

Insulated-gate field-effect-transistor structures , prepared with thin films of lead sulfide as the semiconductor and aluminum oxide as the gate insulator, exhibit greatly improved stability with regard to carrier-trapping effects as compared with other thin-film transistors (TFTs) such as those made of cadmium selenide. The devices are prepared in a series of additive evaporation steps (through stencil masks) in a single pumpdown of the vacuum system. They are n-type but exhibit field-effect inversion to p-type. They are generally enhancement devices but can also be prepared as depletion devices by increasing the time and temperature of the postdeposition anneal. The carrier mobility is of the order of 10 cm²/V-sec, and the carrier concentration is approximately 3 × 10¹⁷/cm³.