Enhanced performance characteristics of n-ZnO/p-GaN heterojunction light-emitting diodes by forming excellent Ohmic contact to p-GaN

Abstract

We report significantly improved performance characteristics of n-ZnO/p-GaN heterojunction light-emitting diodes (LEDs) by forming excellent Ohmic contact to p-GaN. An elaborately designed fabrication procedure to suppress ZnO sputtering damage on p-GaN, i.e., a selective SiO2 passivation of the p-GaN surface, was shown to yield excellent Ohmic contact to p-GaN with a specific contact resistance of 9.8×10−3Ωcm2, while the reference contact formed on non-protected p-GaN showed non-Ohmic behavior. Heterojunction LEDs fabricated with the improved p-Ohmic contact had much better performance characteristics than did the reference LEDs, i.e., the forward voltages at 2mA were 5.6 and 16.2V, the series resistances were 404 and 1693Ω, and the optical output powers at 3mA were 56.4 and 19.9μW for the developed and reference LEDs, respectively.