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GaN基肖特基势垒二极管（SBD）器件具有功率密度高、转换效率高以及开关特性好等优点。GaN材料在异质外延过程中不可避免地会引入大量的位错，而位错会导致器件的可靠性问题。本文报道了一种在自支撑GaN衬底上生长并制备的超低位错密度N+/N- GaN准垂直SBD器件。高分辨X射线衍射仪和原子力显微镜表征结果显示，在自支撑GaN衬底上实现了总位错密度为1.01×108cm-2，表面均方根粗糙度为0.149nm的高质量外延层的生长。基于高质量外延层制备的器件在不使用任何终端、场板以及等离子体处理的情况下，在反向电压为-5V时表现出10-5A/cm2的极低泄漏电流密度，与在蓝宝石衬底上同步制备的对照组器件相比，反向泄漏电流低4个数量级。实验结果表明，基于自支撑GaN衬底的准垂直GaN基SBD能够大幅度降低器件的反向漏电，极大地提升准垂直SBD器件的电学性能。使用微光显微镜对两组器件进行观察，确定了准垂直SBD器件的泄漏电流主要集中在阳极边缘，并解释了漏电机理。最后对器件进行了变温测试，在温度为100℃时，仍表现出低于10-3A/cm3的泄露电流，证明了自支撑GaN衬底上准垂直SBD器件具有优良的应用前景。
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关键词:
- 自支撑氮化镓 /
- 位错密度 /
- 准垂直型肖特基二极管 /
- 电学性能
GaN based Schottky barrier diode (SBD) offer advantages including high power density, high conversion efficiency, and excellent switching characteristics. During heteroepitaxial growth of GaN, a high density of threading dislocations is inevitably introduced, which can degrade device reliability. This paper reports a low dislocation density N+/N- GaN quasi-vertical SBD fabricated on a freestanding GaN substrate. The characterization results of high-resolution X-ray diffraction and atomic force microscopy demonstrate that the high-quality epitaxial layer with a total dislocation density of 1.01×108 cm-2 and a root mean square surface roughness of 0.149 nm has been achieved on a freestanding GaN substrate. Devices prepared based on high-quality epitaxial layer exhibit an ultra-low leakage current density of 10-5 A/cm2 at a reverse voltage of -5V, without employing any edge termination structures, field plates, or plasma treatment. Compared with the devices prepared on sapphire substrates using identical processes, the reverse leakage current demonstrates a reduction by four orders of magnitude. The experimental results show that the quasi-vertical GaN based SBD fabricated on a freestanding GaN substrate significantly reduces reverse leakage current and substantially enhances the overall electrical performance of the device. By employing micro-microscope, leakage current in quasi-vertical SBDs was identified to be primarily localized at the anode edges, and the underlying leakage mechanism was elucidated. Finally, temperature-dependent measurements demonstrated the device maintains a leakage current below 10-3 A/cm2 at 100℃, confirming the potential of quasi-vertical SBD on freestanding GaN substrate for practical applications.-
Keywords:
- freestanding gallium nitride /
- dislocation density /
- quasi-vertical schottky diode /
- electrical properties
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