Charge Transport in Vertical GaN Schottky Barrier Diodes: A Refined Physical Model for Conductive Dislocations

• Published in: IEEE transactions on electron devices 2020-03, Vol.67 (3), p.841-846
• Main Authors: Chen, Leilei, Jin, Ning, Yan, Dawei, Cao, Yanrong, Zhao, Linna, Liang, Hailian, Liu, Bin, Zhang, En Xia, Gu, Xiaofeng, Schrimpf, Ronald D., Fleetwood, Daniel M., Lu, Hai
• Format: Article
• Language: English
• Subjects: Charge transport; Conduction bands; Conductive dislocation; Current measurement; Current voltage characteristics; Field emission; Gallium nitride; Gallium nitrides; GaN Schottky diode; Leakage current; Schottky barriers; Schottky diodes; Substrates; surface donor; Temperature dependence; Temperature measurement; thermionic field emission (TFE); Tunneling
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2020.2965953

Charge transport mechanisms of forward and reverse leakage currents in vertical GaN Schottky barrier diodes are investigated by measuring the temperature-dependent current-voltage characteristics. The results show that the leakage current is primarily governed by dislocation-associated thermionic field emission (TFE). The primary transport path is the reduced, localized conduction band around the dislocation core rather than the continuum defect states. A refined phenomenological physical model is developed for conductive dislocations in GaN, emphasizing that: 1) surface donors, surrounding the core of dislocations, can significantly shrink the barrier region after ionization, causing severe TFE leakage; 2) the ON donors likely to be responsible for TFE have a typical density of ~1 × 10 18 cm -3 at 300 K and activation energy of 78 meV; and 3) the barrier height at donor sites is ~0.65 eV at 300 K, which is reduced by ~0.4 eV with respect to the dislocation-free region.