Influence of Surface Recombination on Forward Current-Voltage Characteristics of Mesa GaN \hbox^\hbox Diodes Formed on GaN Free-Standing Substrates

• Published in: IEEE transactions on electron devices Vol. 59; no. 4; pp. 1091 - 1098
• Main Authors: Mochizuki, K., Nomoto, K., Hatakeyama, Y., Katayose, H., Mishima, T., Kaneda, N., Tsuchiya, T., Terano, A., Ishigaki, T., Tsuchiya, R., Nakamura, T.
• Format: Journal Article
• Language: English
• Published: IEEE 01-04-2012
• Subjects: Current measurement; Gallium compounds; Gallium nitride; Photonics; power semiconductor devices; Recycling; Schottky diodes; simulation; Surface treatment
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2012.2185241

The influence of surface recombination on forward current-voltage (I F -V F ) characteristics of gallium nitride (GaN) p + n diodes formed on GaN free-standing substrates was both experimentally and computationally investigated. In the temperature range of 373-273 K, the surface-recombination velocity 5 of 0.5-μm n GaN overetched circular-mesa diodes was derived, respectively, as 2-10 × 10 7 and 1 × 10 7 cm/s for diodes with and without a mesa-field-plate termination structure consisting of dielectric and metal layers. It was shown that IF (V F <; 2.9 V) is dominated by carrier recombination at the side surface of the etched n GaN. The I F -V F characteristics of the fabricated diodes were compared with the reported GaN p + n diodes with almost-zero overetched depth of n - GaN. The large I F of the latter diodes is attributed to enhanced photon recycling through photon reflection at the metal mirror. Moreover, reducing S to less than 10 5 cm/s is considered indispensible for achieving similar enhanced photon recycling in overetched terminated diodes.