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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.
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Keywords:
- freestanding gallium nitride /
- dislocation density /
- quasi-vertical schottky diode /
- electrical properties
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