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The enhanced conduction at low fields (

We propose two models of electron tunneling from metal to a semiconductor via traps. In addition to the electrons below the metal Fermi level, the models also include the thermally activated electrons above the Fermi level. The first model is called generalized thermionic trap-assisted tunneling (GTTT), which considers tunneling through both triangular and trapezoidal barriers present in metal insulator semiconductor (MIS) structures. The second model is called thermionic trap-assisted tunneling (TTT), which considers tunneling through triangular barriers present in modern Schottky junctions. The GTTT model is shown to predict the low field leakage currents in MIS structures with nitrided oxide as insulator, and the TTT model is shown to predict the reverse gate leakage in AlGaNGaN high electron mobility transistors. � 2006 American Institute of Physics.

The off-state gate current in AlGaN/GaN high electron mobility transistors is shown to arise from two parallel gate to substrate tunneling paths: a direct path, and a path via deep traps, which are distributed throughout the AlGaN layer and spread over an energy band. A model to calculate this current is given, which shows that trap-assisted tunneling dominates below T∼500 K, and direct tunneling (thermionic field emission) dominates at higher temperatures. A model fit to experimental results yields the following fabrication process sensitive parameters: trap concentration of ∼1013–1015 cm−3, and trap bandwidth of ∼50%–70% of the barrier height located 0.4–0.55 V below the conduction band edge.