Search

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.

We report a simple closed-form model of the total emission through a triangular potential barrier due to thermionic field emission (TFE) and field emission (FE). Such a model has not been derived previously, since the energy distribution function of emitted electrons is not analytically integrable. We overcame this difficulty using a geometrical approximation of the integration operation. Our model so derived reveals the energy location and spread of the emission, which allow estimation of the emission through any fraction of the barrier. It also yields a characteristic field parameter in terms of the barrier height, temperature, and effective mass, which can be used to identify the TFE, FE, and TE regimes of device operation.

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.