JUNCTIONS AND THIN FILM TRANSISTORS

The metal semiconductor barrier has been extensively studied since its discovery by Schottky,
Stormer and Waibel. The rectifying behaviour of this structure was independently interpreted
by Schottky [1] and Mott [2], in crystalline semiconductors. Concerning amorphous silicon
(a-Si:H) Schottky barriers, the behaviour expected is quite different from that observed in
crystalline semiconductors where the charge density in the depletion region is only determined
by shallow donors or acceptors. Here, the barrier behaviour is highly dependent on: (1) surface
finishing and the presence, or not, of a native oxide [3]; (2) shallow and bulk density of states
[4]; (3) charges associated with localised states in the gap; (4) carrier losses due to
inhomogeneities in the metal Schottky contact [5] and losses related to the neutral and depletion
regions.