Analysis of Vertical GaN JBS and p-n Diodes by Mg Ion Implantation and Ultrahigh-Pressure Annealing
Shane Stein, Dolar Khachariya, Will Mecouch, Seiji Mita, Pramod Reddy, James Tweedie, Kacper Sierakowski, G. Kamler, Michał Boćkowski, E. Kohn, Zlatko Sitar, Ramón Collazo, Spyridon Pavlidis
Abstract
We report on vertical GaN junction barrier Schottky (JBS) diodes formed by Mg ion implantation and ultrahigh -pressure annealing (UHPA). The static ON-state characteristics of the diodes show an ideality factor of 1.05, a turn-on voltage of ~0.7 V, a current rectification ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10^{11}$ </tex-math></inline-formula> , and a low differential specific ON-resistance that scales with Schottky stripe width in fair agreement with the analytical model. The reverse leakage dependence on Schottky stripe width also agrees well with the analytical model. Implanted p-n junction diodes fabricated on the same wafer exhibit avalanche breakdown in reverse bias with a positive temperature coefficient, but the forward current is limited by a series barrier. Temperature-dependent current–voltage measurements of th p-n diodes verify the presence of the implanted p-n junction and reveal an additional 0.43-eV barrier, which we hypothesize arises from a p-Schottky contact and forms a second diode back-to-back with the p-n junction. This interpretation is supported by analysis of the capacitance–voltage characteristics of the implanted p-n diodes, epitaxial p-n diodes fabricated with intentional p-Schottky contacts, and comparison to TCAD simulations. Ultimately, the presence of the p-Schottky contact does not hinder JBS diode operation. The use of diffusion-aware designs and/or diffusion reduction represents future directions for Mg implantation technology in GaN power devices.