Vertical GaN junction barrier Schottky diodes with near-ideal performance using Mg implantation activated by ultra-high-pressure annealing

Abstract

We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, a turn-on voltage of 0.75 V, and a specific differential ON-resistance of 0.6 mΩ·cm2. The breakdown voltage of the JBS diode is 915 V, corresponding to a maximum electric field of 3.3 MV/cm. These results underline that high-performance GaN JBS can be realized using Mg implantation and high-temperature UHP post-activation anneal.

Schottky contacts on ultra-high-pressure-annealed GaN with high rectification ratio and near-unity ideality factor

“…Hall effect and X-ray photoelectron spectroscopy (XPS) data are also analyzed to examine possible bulk-or surface-based factors that influence contact behavior. We then demonstrate Schottky contacts with high rectification ratio, near-unity ideality factor, and high homogeneity by using a surface treatment to recover the surface after UHPA prior to contact deposition, paving the way for high-performance ion-implanted vertical GaN JBS diodes, as we have recently reported elsewhere, 8) as well as other devices in the future which require selective area doping. 2) 1 μm thick n − -GaN epitaxial films were grown on ammonothermal n + -GaN substrates using a vertical, coldwall, radio frequency-heated, low-pressure metalorganic chemical vapor deposition (MOCVD) reactor.…”

“…23) The demonstration of highly ideal Schottky contacts on UHP annealed n-GaN is a critical milestone achievement for the development of GaN devices requiring selective area doping, 2) and is a key enabling factor in our recent demonstration of record-performance vertical GaN JBS diodes fabricated via ion implantation and UHPA. 8) In conclusion, Ni contacts deposited on n-type GaN following UHPA suffer from degraded Schottky characteristics, exhibiting high leakage current greater than 0.1 A cm −2 , which is prohibitive to the fabrication of JBS diodes capable of high blocking voltage. Hall effect measurements show no significant change in bulk doping concentration of the annealed films.…”

“…7) Prospective GaN power devices include the metal-oxidesemiconductor field-effect transistor, 5) junction field-effect transistor, 2,6) and junction barrier Schottky (JBS) diode. [8][9][10] These devices, as well as edge terminations such as junction termination extension or floating guarding rings necessary for high blocking voltage, require selective area doping. Ion implantation is an established method for selective area doping in other semiconductors, but its translation to GaN technology is challenging since GaN is prone to surface decomposition when annealed at the high temperatures necessary for dopant activation and damage recovery after implantation.…”

Ga-polar GaN Camel diode enabled by a low-cost Mg-diffusion process

“…The vast literature indicates that GaN SBDs with standard Schottky metal (such as Ni) exhibit a f B and turn-on voltage (V turn-on ) of ∼0.7-1.0 eV and ∼0.5-0.8 V, respectively. [12][13][14][15][16][17][18] A low f B promotes the field emission (FE) and thermionic FE (TFE) of electrons leading to a large reverse current and early onset of the reverse breakdown in SBDs. 19,20) For instance, the theoretical breakdown voltage of GaN SBDs with V turn-on of ∼0.7 V is expected to be less than 900 V. 14) In contrast, GaN PN junction (bipolar) diodes offer a larger f B (and hence a larger breakdown voltage) with compromised operation speed.…”

“…On the other hand, processes such as ion-implantation readily degrade the film quality and demand ultra-high-pressure annealing conditions. 18,26,27) Interestingly, unipolar Camel diodes have been extensively investigated for lower bandgap semiconductors, [28][29][30][31] whereas only a handful of reports are available for GaN Camel diodes. 22,32) In this study, we report on a Ga-polar GaN Camel diode realized by employing a low-cost Mg diffusion process.…”