The improvement of selective-area growth using plasma assisted molecular beam epitaxy for low ohmic contact resistance

To achieve very low ohmic contact resistance, n⁺-GaN layer was selectively deposited using plasma assisted molecular beam epitaxy. During this process polycrystalline GaN grew on the patterned SiO₂ region which was subsequently removed by a heated KOH solution, resulting in damage on the n⁺-GaN surface. To prevent this damage, an additional SiO₂ layer was selectively deposited only on the n+-GaN region, producing a specific contact resistance (4.59 x 10^-7 Omega-cm²) much lower than that with the KOH etching damage (4.92 ~ 23.7 x 10^-6 Omega-cm²). Each of KOH etching included large pits (4.08 x 10⁸ cm^-2) and degraded current transport.