Research Of Technology To Improve Breakdown Voltage And Novel Structure Of Enhancement GaN HEMT

Wide band gap semiconductor Gallium Nitride（GAN） is a typical third generation semiconductor materials,which has a high band gap（3.4ev） and high critical breakdown electric field（3.3MV/cm） and electron saturation velocity（2.5×107cm/s）. GaN based heterogeneous high electron mobility transistor（high electron mobility transistor, HEMT） has high concentration and high mobility rate of the two-dimensional electron gas（2DEG）. Thus it has a great application prospect in the field of high frequency, high power and low power consumption. Therefore, the focus of this paper is to study the fluoride ion buried GaN HEMT to improve the breakdown voltage, mechanism, and its process simulation. Study the mechanism and properties of the self biased field plate AlGaN/GaN HEMT. The main contents include:（1） Proposed a new structure of AlGaN/GaN buried layer HEMT with fluoride. First of all, introduced the effect of fluorine ion buried layer in the device. Through the introduction of the high concentration of fluoride ions in the AlGaN barrier layer to achieve enhancement mode; the FG buried layer beneath the gate, on the one hand lifting the threshold voltage of the device; on the other hand lifting in the conduction band height. Therefore, in the reverse voltage, the electron barrier stops source electronic to the high field region at the gate edge. The electron impact ionization can be reduced effectivelly, avoiding the premature avalanche breakdown. The fluorine ion in the drift region of the buried layer FD expands the width of the depletion region, reducing the peak electric field on the drain side of the gate. The distribution of electric field in the drift region is optimized by the FD, improving the breakdown voltage further. Secondly, the fluorine ion implantation energy and dose ar ediscussed, as well as the selection and production of metal Schottky gate. To sum up, the new device is superior to conventional HEMT breakdown voltage is increased by 3 times, and effectively inhibited the effect of DIBL with good performance.（2） The self biased field plate technology is presented. Based on this technique presents self bias field plate AlGa N/GaN HEMT（SBFP-HEMT）. SBFP-HEMT device structure and mechanism are described in detail, focusing on single bias field plate SBFP-HEMT and double bias field plate SBFP-HEMT parameters of the simulation optimization. The simulation results show that the single bias field plate SBFP-HEMT, VFP=100 V, L1=5, L_FP=1 μm has the maximum breakdown voltage 665 V. For dual bias field plate SBFP-HEMT. The maximum breakdown voltage is 978 V when the L1=1 μm, L2=1 μm, L_FP1=1 μm, V_FP1=240V, V_FP2=500V. The breakdown voltage from the conventional floating field plate HEMT’s 552 V improve to 978V（breakdown voltage of increased by 77%）, and the maximum output current only lower 1.3% than that without field plate structure. This showed that, under the premise of not reducing the device performance and significantly improve the breakdown voltage of the device by using the new self bias field plate technology in the SBFP-HEMT device.