Atomic-Level Control of SiC and Device Applications

碳化硅（SiC）是一种具有宽禁带的ⅳ-ⅳ化合物半导体材料。碳化硅的宽带隙使材料的击穿场非常高，大约是硅或砷化镓的十倍。在SiC中，光学声子的能量高达100-120meV，具有高的饱和电子漂移速度（6H-SiC中为2 × 10^7 cm/s）和高导热系数（4.9W/Kcm）。这些优异的性能和晶体生长过程中可控的p型和n型掺杂使SiC成为一种非常有吸引力的半导体材料。研究了碳化硅（SiC）在SiC{0001}衬底上的化学气相沉积（CVD）及其器件应用。本文提出了一种多型控制的SiC外延生长方法，即在离取向SiC{0001}衬底上利用阶梯流生长（阶梯控制外延），并详细讨论了生长机理。在阶梯控制外延中，碳化硅的生长受到停滞层中反应物扩散的控制。使用描述SiC在邻近{0001}衬底上生长的模型，预测了生长模式从阶梯流转变为二维成核的关键生长条件。研究了碳化硅薄膜表面的阶跃聚束、成核和阶跃动力学。通过低温光致发光、霍尔效应和深能级测试，阐明了SiC薄膜的高质量。通过原位掺杂氮给体和铝/硼受体，在较宽的范围内获得了优异的掺杂可控性。研究了步控沉积层在碳化硅器件制造中的最新进展。SiC的内在潜力在大功率、高频和高温SiC器件的优异性能中得到了证明，这将开拓新的电子学领域。

Silicon carbide (SiC) is a IV-IV compound semiconductor material with a wide bandgap. The wide bandgaps of SiC give the material very high breakdown field, about ten times higher than that of Si or GaAs. The energies of optical phonons in SiC are as high as 100-120meV,which leads tohigh saturated electron drift velocity (2x10^7 cm/s in 6H-SiC) and high thermal conductivity (4.9W/Kcm). These outstanding properties and controllable p- and n-type doping during crystal growth make SiC a very attractive semiconductor material. Chemical vapor deposition (CVD) of silicon carbide (SiC) on SiC {0001} substrates and device applications have been investigated. Polytype-controlled epitaxial growth of SiC,which utilizes step-flow growth on off-oriented SiC {0001} substrates(step-controlled epitaxy), isproposed, and the detailedgrowth mechanism is discussed. In step-controlled epitaxy, SiC growth is controlled by the diffusion of reactants in a stagnant layr. Critical growth conditions where the growth mode changes from step-flow to two-dimensional nucleation are predicted as a function of growth conditions using a model describing SiC growth on vicinal {0001} substrates. Step bunching on the surfaces of SiC epilayrs, nucleation, and step-dynamics are also investigated. High quality of SiC epilayrs was elucidated through low-temperature photoluminescence, Hall effect, and deep level measurements. Excellent doping controllability in the wide range has been obtained by in-situ doping of a nitrogen donor and aluminum/boron acceptors. Recent progress in SiC device fabrication using step-controlledepitaxial layrs is studied. Intrinsic potential of SiC has been demonstrated in the excellent performance of high-power, high-frequency, and high-temperature SiC devices, which will exploit novel electronics.