Planar GaN p-i-n photodiodes with n⁺-conductive channel formed by Si implantation

In this study, planar GaN p-i-n photodiodes (PDs) were fabricated by Si implantation into GaN-based p-i-n structure grown by metal organic vapor-phase epitaxy. Triple silicon implantation was performed to form a selective n+ channel through the multilayer p-i-n structure. As a result of n+ -channel formation, a planar GaN p-i-n detector could be obtained. With the reverse bias below 2 V, the dark current density was well below 50 pA. The dark current increased significantly with an increase of reverse bias, which may be attributed to the incomplete damage (from implantation) removal and thereby result in the higher leakage current. The typical peak responsivity and the cutoff wavelength for the Si-implanted planar p-i-n PDs were around 0.13 AW and 365 nm, respectively. In addition, the visible (450 nm) -to-UV (365 nm) rejection ratio of around three to four orders could be extracted from the spectra response. Furthermore, the transient response measurements revealed that the full width at half maximum (FWHM) of impulse response was as low as 1.12 ns.