Control of Electronic Properties of Wide Bandgap Semiconductor and Application to Energy Electronics

在本研究项目中，研究了宽带隙SiC的高质量外延生长，其性能和MOS（金属氧化物半导体）接口的控制，以及在大功率器件中的应用。通过使用高纯度和高质量的SiC涂层，实现了在10^<14>到10^<20>cm^<-3>范围内的电导率控制。对离子注入选择性杂质掺杂进行了系统的研究。获得了n型和p型的低片电阻分别为105Ω/□和3600Ω/□。研究了MeV离子注入形成的深pn结和V离子注入形成的半绝缘SiC层。在n型和p型SiC上对MOS电容器进行了详细的表征，揭示了氧化条件与MOS界面质量之间的明确关系。碳化硅mosfet中反转通道的迁移率可由浅层类受体界面态引起的电子俘获和负电荷控制。通过使用（1120）的新型晶面，通道迁移率从5cm^2/Vs提高到96cm^2/Vs。SiC (1120) MOSFET的通道迁移率首次显示为负温度系数，这对功率MOSFET的应用至关重要。各种高压碳化硅器件已成功制成。Ni/SiC肖特基二极管的击穿电压为1630V，导通电阻低至5mΩcm^2。外延平台和植入的平面SiC引脚二极管分别表现出4200V和4600V的高击穿电压。SiC引脚二极管击穿电压随温度升高而升高，表明雪崩击穿。横向高压（700V） SiC mosfet也已被证明。

In this research project, high-quality epitaxial growth of wide bandgap SiC, control of its properties and MOS (metal-oxide-semiconductor) interfaces, and applications to high-power devices have been investigated. By using high-purity and high-quality SiC epilayers, conductivity control has been realized in the wide range from 10^<14> to 10^<20>cm^<-3>. Selective impurity doping by ion implantation has been systematically investigated. Low sheet resistances of 105Ω/□ for n-type and 3600Ω/□ for p-type were obtained. Formation of deep pn junction by MeV ion implantation and semi-insulating SiC layers formed by V ion implantation were also investigated.Detailed characterization of MOS capacitors on n- and p-type SiC revealed clear relationship between oxidation condition and MOS interface quality. The inversion channel mobility in SiC MOSFETs may be controlled by the electron trapping and negative charge caused by shallow acceptor-like interface states. The channel mobility has been improved from 5cm^2/Vs up to 96cm^2/Vs by utilizing a novel crystal face of (1120). The channel mobility for SiC (1120) MOSFETs showed a negative temperature coefficient for the first time, which is critical for power MOSFET applications.Various high-voltage SiC devices have been successfully fabricated. Ni/SiC Schottky diodes exhibited a 1630V breakdown voltage together with a low on-resistance of 5mΩcm^2. Epitaxial mesa and implanted planar SiC pin diodes showed very high breakdown voltages of 4200V and 4600V, respectively. The breakdown voltages of SiC pin diodes increased with increasing temperature, indicating avalanche breakdown. Lateral high-voltage (700V) SiC MOSFETs have been also demonstrated.