Growth and Fabrication of High Breakdown Voltage AlGaN/GaN Metal-Insulator-Semiconductor Field Effect Transistors

• Main Authors: Chien-Yu Pao, 鮑建佑
• Other Authors: Jen-Inn Chyi
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/90361289417894008956

碩士 === 國立中央大學 === 電機工程學系 === 102 === This thesis focus on the enhancement of off-state breakdown voltage of AlGaN/GaN Metal-Insulator-Semiconductor Field Effect Transistors (MIS-FETs) by using MOCVD grown different epitaxy structures on Si. With increasing GaN buffer layer up to 4.6 μm thick, the fabricated AlGaN/GaN MIS-FETs off-state breakdown voltage is up to 960 V at LGD = 20 μm, while the 2.5 μm GaN thick buffer layer has 795 V device breakdown voltage. However, with increasing buffer layer thickness, the edge crack extends to 1.5 cm, which means only 65% area of 6-inch silicon substrate is available. For the purpose of enhance wafer area efficiency, several ways were surveyed to improve devices characteristics without extend buffer layers thickness. The first selection is 5% Al-content AlGaN as buffer layer. 5% AlGaN has off-state breakdown 705 V while GaN buffer layer equips 795 V, which was because dislocation densities serious affect off-state leakage path and breakdown voltage, growth condition of 5% AlGaN need to be optimized. From previous results, that is the dislocation densities seriously affect device off-state characteristics, the growth of AlN interlayer experiment was designed for enhancing epitaxial quality. Which improved the devices breakdown voltage from 795 V to 926 V, about 16% breakdown voltage enhancement. Furthermore, off-state I-V curve of the devices fitted the theory of Space Charge Limited Current, which advanced understanding of the cause of the devices off-state leakage current formation.