Buffer leakage induced pre-breakdown mechanism for AlGaN/GaN HEMTs on Si

An off-state breakdown mechanism of a silicon based AlGaN/GaN High-Electron-Mobility Transistor (HEMT) is proposed. Through physical-based 2D simulations, leakage current model of this breakdown mechanism including AlN/Si interface inversion layer channel and local trap tunneling effect in the buffer layer is proved. Results show that the interfacial inversion based leakage current in the buffer can drastically weaken the V_B to 50V for GaN-On-Silicon devices with L_GD = 5 μ m thus causing detrimental problems for HEMTs applications. Further design of the GaN-On-Silicon HEMT with an enhanced back barrier layer shows an effective suppression of the leakage current. Simulation result shows a significantly increase of the V_B up to 672 V for an optimized structure with the same physical dimensions as the convention device.