InAlN/GaN HEMT Device Design And Modeling

Power semiconductor devices are widely used in power management, consumer electronics, power transmission, have a profound influence on human life. Silicon semiconductor device have been developing decades, and their performance is approaching the theoretical limits of the material, while the rapid development of electronic systems need higher performance power devices, this forcing researchers to try new semiconductor materials imminent. Gallium nitride(GaN) compound semiconductor material have the merits of wide bandgap, high electron saturation velocity, large critical breakdown field, which enables GaN high electron mobility transistor(HEMT) to keep fast switching speed, low conduction resistance and high breakdown voltage.In AlN/GaN heterojunction could be obtained with lattice-match when the barrier layer mole fraction of InN of 17%, effectively increasing device reliability. InAlN/GaN can achieve super high concentration 2DEG due to strong spontaneous polarization effect, which greatly increase the device current density, proves to be a promising nextgeneration power device. However, InAlN/GaN HEMT still faces many challenges, such as current collapse, leakage suppression, reliable technology for enhancement-mode device, as well as improve the quality of the wafer material. The main contents of this thesis as the following:1. Based on relevant references, theoretically analysis the polarization of GaN heterojunction and the mechanism of the GaN-based HEMT as well as the methods of achieving enhancement-mode GaN HEMT. Systematically discussed the causes and methods of inhibiting of current collapse of GaN HEMT. Based on the work in IMECAS and SINANO and the available references, this thesis also introduce the major process of GaN HEMT.2. Recess gate and negative charges implanted into gate region enhancement-mode technology for InAlN/GaN HEMT are studied by Sentaurus simulation platform. The variation with recess depth and density of negative charges for transfer characteristics of the HEMT are analyzed, what’s more, a gate recess InAlN/GaN threshold voltage analytical modal is built by studying the bandgap structure.3. In AlN/GaN HEMT with Schottky source(SS) technology were used, conventional source ohmic contact metal replaced by low workfunction Schottky metal. The source metal of SS HEMT avoid high temperature annealing and effectively improved the metal morphology which can reduce leakage and improve breakdown voltage. This thesis study SS InAlN/GaN HEMT for improving breakdown voltage compare to conventional HEMT by computer simulation, and then tapeout experiment accomplished for SS In AlN/GaN HEMT, devices test show the SS can reduce leakage and enhance breakdown voltage.