High-Efficiency Nitride-based Power Devices in the Next Generation

本项目的目的是证明III族氮化物是制作下一代大功率FET的最合适的材料之一。在2006财年，1.通过表面钝化降低导通电阻和改善互导；2.逆变电路中亚阈值摆动小、功耗低；3.通过改变势垒成分和厚度来控制阈值电压；4.阐明了栅源和栅下迁移率的差异。为了实现高功率器件，衬底具有极小的晶格失配和极高的电阻，因此具有广阔的应用前景。因此，在本项目中，5.用升华法在6H-SiC衬底上生长AlN衬底，6.用高温MOVPE在蓝宝石衬底上生长高质量的AlN模板。在2007财年，我们发现了SiN钝化膜厚度与最大漏电流之间的关系。通过将SiN厚度优化为5 nm，实现了以下性能：最大漏电流密度：1.58×10；-1；[A/mm]，漏电流：1.45×10；-8；[A/mm]，通断比大于7个数量级，亚阈值摆幅：90[mV/dec.]，导通电阻：3.4[mΩcm^2]。此外，击穿电压高达325V，足以满足小型空调逆变电路的需要。

Objective of this program is to prove that the group III nitride is one of the most suitable materials for the fabrication of high power FET in the next generation. In FY2006, 1. Reduction of on resistance and improvement of the mutual conductance by surface passivation, 2. Small sub-threshold swing and low power loss in inverter circuit, 3. Controllability of the threshold voltage by changing barrier composition and thickness, and 4. Difference of the mobility underneath the gate-source and the gate were clarified. In order to realize high power devices, AN substrate is very promising because of the small lattice mismatch and the extremely high resistance. Therefore, in this program, 5. Growth of AIN substrate by sublimation on the 6H-SiC substrate, and 6. Growth of high quality AIN template on a sapphire substrate by high temperature MOVPE was conducted. Several papers were published for this issue.In FY2007, relationship between thickness of SiN passivation film and the maximum drain current was found. By optimizing the SIN thickness to be 5 nm, the following performance can be successfully observed in the normally off JHFET; Maximum drain current density: 1.58×10^<-1> [A/mm], leakage current: 1.45×10^<-8> [A/mm], on/off ratio: higher than 7 orders of magnitude, sub-threshold swing: 90 [mV/dec.], on resistance: 3.4 [mΩcm^2]. In addition, breakdown voltage was as high as 325 V, which is sufficient for inverter circuits for small size air conditioner.