Optical-Thermo-Transition Model of Reduction in On-Resistance of Small GaN p–n Diodes

The forward current (I F) of GaN p–n diodes forward biased at 5 V was found to be proportional to anode perimeter and independent of temperature (273–373 K). Although this I F characteristic contributes to reduction in specific on-resistance (R on A) of small GaN p–n diodes, the mechanism involved is yet to be understood. Accordingly, in this study, an optical-thermo-transition model for the reduced R on A in small GaN p–n diodes is proposed. The energy of photons that are created through radiative recombination around the edge of anode electrode is considered to be used for optical-thermo-transition; that is, electrons are emitted from ionized acceptors to conduction bands, and the resultant neutralized acceptors are ionized through electron capture from valence bands. Since known self-heating and intrinsic-photon-recycling effects are considered to be negligible, optical-thermo transition and enhanced radiative recombination (due to large perimeter-to-area ratio) are concluded to play a dominant role in reducing R on A.