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Local p-type doping in GaN is a key issue for device development but it remains a challenge to be achieved. In this work, we studied the activation of Mg implanted in the GaN. Multi-energy implantations were performed to achieve a 'box-like' profile. SIMS measurements showed unexpected deep Mg profile due to defect-assisted channeling in the GaN. In addition, a high-density defect region induced by the implantation was evidenced by TEM characterization. To protect the GaN surface prior to high temperature annealing, an AlN cap-layer was deposited by reactive sputtering followed by SiO x deposition leading to a double cap-layer. Afterwards, the capped samples were RTA-annealed at high temperatures for several minutes under nitrogen. Two types of annealing processes were applied: a monocycle and a multicycle annealing. After annealing, the double cap-layer was etched using chemical solutions. AFM characterizations, after annealing and cap-layer etching, demonstrated that a GaN surface with similar roughness to as-grown samples and pit-free can be achieved after both monocycle and multicycle annealing steps. However, an AlGaN layer at the AlN/GaN interface is observed by ToF-SIMS and remained after the etching of the AlN layer. Finally, Schottky diodes were processed on the unimplanted and annealed samples, evidencing a double barrier, while P/N junction diodes are still being processed on the implanted and annealed samples. [ABSTRACT FROM AUTHOR]

Efficient edge terminations are fundamental for power electronic devices. High resistive edge termination technique obtained by ion implantation is a possible solution for GaN Schottky barrier diodes (SBD), but may induce defects detrimental to the devices. In this work, two sets of GaN SBDs, with or without a high resistive guard ring edge termination, were investigated by deep levels transient spectroscopy (DLTS). The corresponding DLTS spectra of devices with guard ring were compared to those of as-fabricated devices (without). Four deep traps at 0.13, 0.26, 0.35, and 0.51 eV were observed below the conduction band in as-fabricated structures while the ones with guard ring exhibit two additional levels at 0.47 and 0.80 eV and a strong enhancement in DLTS peaks magnitude. Further investigations showed that the additional traps detected in SBD devices with guard ring were consistent with ion implantation-induced damages. These observations highlight the impact of high resistive edge termination technique on our devices and raise the need of optimization of such crucial structure for the improvement of GaN-based Schottky barrier diode. [ABSTRACT FROM AUTHOR]

In this work, both “Schottky to Schottky” structure (STS) and pseudo-vertical Schottky barrier diode (pv-SBD) have been processed on GaN heteroepitaxially grown on sapphire or silicon by metal organic chemical vapor deposition (MOCVD) and characterized physically and electrically. Ni and Ti/Al were used to obtain respectively Schottky and Ohmic contacts using rapid thermal annealing (RTA). Adequate passivation steps and insertion of a resistive guard ring were also implemented in pv-SBD. The STS results, presented in this paper, evidence the impact of the substrate on the growth as well as all the progresses that have been done on GaN material quality. Furthermore, we demonstrate that high quality Schottky diodes can be obtained on GaN grown on sapphire by MOCVD. Indeed, ideality factors of 1.09 as well as a barrier height of 1.06 eV were obtained on pv-SBD devices that have a breakdown voltage over 600 V. [ABSTRACT FROM AUTHOR]