Interface DOS dependent analytical model development for DC characteristics of normally-off AlN/GaN MOSHEMT

In this paper a charge controlled analytical model is developed to predict quantum capacitance, threshold voltage and drain current for normally-off AlN/GaN Metal Oxide Semiconductor High Electron Mobility Transistor (MOSHEMT). The oxide/semiconductor interface Density of State (DOS) dependent model for two dimensional electron gas (2DEG) density is obtained by demonstrating necessary energy band diagrams. Quantum capacitance in the channel and threshold voltage is obtained by using different boundary conditions. By using these expressions the drain currents in both linear and saturation mode are derived. It is interesting to note that a positive threshold voltage necessary for normally-off operation can be obtained by decreasing the AlN barrier thickness below a critical value. The predicted DC characteristics are in good agreement with the experimental results, thus it confirms the validity of the proposed model.