以Silvaco模擬器模擬高功率氮化鋁鎵/氮化鎵蕭特基二極體陽極邊緣效應

Abstract

本研究中，專注高功率氮化鋁鎵/氮化鎵蕭特基二極體的陽極邊緣效應模擬，包括陽極深掘式、陽極電場板和陽極保護環等結構。利用Silvaco模擬器，輔助模擬各種不同結構與條件，測試陽極邊緣效應，比較對元件的順向導通電壓(流)及逆向崩潰電壓(流)的影響，研究結果顯示因陽極構造的改變，會對陽極表面電場產生影響，或是會改變特定位置的漏電流及電場大小，進而影響元件之崩潰電壓。 本研究利用深掘式陽極結構，以提高蕭特基二極體的導通後順向電流(Forward current)。模擬結果顯示，將Anode向AlGaN層深入後，僅能提高少量順向電流並增加崩潰電壓，估計應為Anode接觸面積增加不大所影響。 本研究利用電場板式和保護環式陽極結構，以提高蕭特基二極體的崩潰電壓(Breakdown voltage)。模擬結果顯示，將陽極自350nm提高至1400nm，並以電場板式自0.1um延長至3.0um，另以保護環式自深度2.5nm延伸至7.5nm，並施以摻雜濃度自1.0*1017/cm3增加至2.0*1018/cm3，均可大幅增加崩潰電壓，而對順向電流較無影響。

Simulation study of anode edge termination on high performance AlGaN/GaN Schottky diodes was performed in this work. The DC performance of devices containing three different anode types, e.g., recess, field-plate and guard-ring, under forward and reverse bias conditions were investigated. Analytical results indicated that the change of anode structure dramatically affects the surface electrical field and, hence, the DC performance of device. It caused the change the leakage current, the electrical field as well as the breakdown voltage of devices. Recess anode structure was adopted for the increase of forward current of Schottky diode. Simulation results revealed a slight increment of forward current and obvious increase of breakdown voltage in the device containing such an anode structure due to the increase of contact area and reduction of AlGaN layer thickness. The improvement of breakdown voltage was investigated in the Schottky diodes containing field-plate and guard-ring anode structures. Compared with the variation of forward current in device samples, we observed much obvious changes in the breakdown voltage for those devices. The breakdown voltages could be substantially improved by increasing the height of anode type from 350 to 1400 nm, the width of field-plate anode type from 0.1 to 3 m, the p-type doping concentration from 11017 to 21018 cm3 with the peak concentration in the depth from 2.5 to 7.5 nm for guard-ring anode type.