A novel surface treatment for the sliver ohmic contacts to P-GaN

Abstract

With the development of the GaN-based light-emitting diodes (LEDs), the need for p-GaN contacts with low resistivity, good thermal stability, and high reflectivity has become more urgent. In this paper, a novel method of surface treatment on p-GaN to form good ohmic contacts between p-GaN and Ag was proposed. We proposed a novel structure with Ag/ultrathin-ITO/p-GaN contact which shows a low contact resistivity as well as a high reflectance attributed to some isolated islands of ITO and the absence of Ni layer. The calculated ρc of the new structure which is lower than 7×10−2W/cm2 based on the CTLM method showed that the Ag/ultrathin-ITO/p-GaN contact has a lower contact resistivity compared to the contact without the ultrathin ITO layer of which the ρc is higher than 2 W/cm2 The Ag film cannot be ripped off by the tape which shows a good adhesion. The LEDs fabricated with this contacts showed a 30% higher luminance at 20mA forward currents as compared to the conventional LEDs.