Investigation of Ni/Ag contact to p‐GaN with an O2 plasma treatment and its application to GaN‐based LEDs

Abstract

AbstractIn this paper, the contact structure of Ni–Ag/p‐GaN with different O2 plasma treatment times for 1 and 5 min was utilized for investigation. From experimental results, the Ni–Ag contact to p‐GaN with different O2 plasma treatment for 1 and 5 min reveals Schottky behaviors. Based on the variation of the specific contact resistance with respect to temperature, the dominant transport mechanism of Ni–Ag/p‐GaN structure presented form thermionic emission to field emission as increasing time from 1 to 5 min. From the X‐ray photoelectron spectroscopy (XPS) results, the increase of the N vacancies and antisite defects (ON) would enhance the resistance of the treated p‐GaN underneath the contact, which would make the Ni–Ag/p‐GaN contact reveal Schottky behavior. With a 20 mA current injection, the operation voltage of light‐emitting diodes (LEDs) with Ni/Ag contact to p‐GaN through O2 plasma treatment 400 W–5 min was 3.13 V larger than the LEDs with Ni/Ag contact to p‐GaN through O2 plasma treatment 400 W–1 min. This is due to the larger specific contact resistance. The 3.13 V operation voltage is still good and acceptable. Furthermore, the largest output power among all devices can be achieved. Besides, the reliability is still good.