High-performance (Al,Ga)N-based solar-blind ultraviolet p–i–n detectors on laterally epitaxially overgrown GaN

Abstract

Solar-blind ultraviolet photodiodes with a band-edge wavelength of 285 nm were fabricated on laterally epitaxially overgrown GaN grown by metalorganic chemical vapor deposition. Current–voltage measurements of the diodes exhibited dark current densities as low as 10 nA/cm2 at −5 V. Spectral response measurements revealed peak responsivities of up to 0.05 A/W. Response times for these diodes were measured to be as low as 4.5 ns for 90%-to-10% fall time. For comparison, diodes were fabricated using the same p–i–n structure deposited on dislocated GaN. These diodes had dark current densities many orders of magnitude higher, as well as a less sharp cutoff, and a significant slow tail under impulse excitation.

High responsivity in molecular beam epitaxy grown β-Ga2O3 metal semiconductor metal solar blind deep-UV photodetector

“…III-nitride alloys (AlGaN), which have been widely explored [12][13][14][15][16] for solar blind UV detection, suffer from lack of native substrates which is a major bottleneck to achieving superior material quality. In contrast, large area single crystal Ga 2 O 3 substrates can be grown from the melt by various conventional crystal growth techniques 17,18 with much superior crystal quality providing an economic and performance advantage.…”

“…6 Fig . 5 illustrates the plot of the responsivity versus dark current for the state-of-the-art solar blind (230-290 nm) UV detectors reported [4][5][6]8,[10][11]16,[30][31][32][33][34][35][36][37] for the devices based on Al x Ga 1-x N as well as on β-Ga 2 O 3 . The detectors reported in this work have excellent responsivity while maintaining a very low dark current for 230-240 nm range.…”

Indium–silicon co-doping of high-aluminum-content AlGaN for solar blind photodetectors

“…Recently, AlGaN p -i -n photodiodes were reported. 4,[5][6][7] The p -i -n device geometry for solar-blind AlGaN detectors has several shortcomings. First, p-type doping of AlGaN layers with a high-Al content remains a difficult problem.…”

“…5 The resistance of ohmic contacts to p-type AlGaN layers is quite high. This resistance can be avoided by using p GaN and or both p GaN and n GaN as the contact layers 4,6,7 with i Al x Ga 1Ϫx N ͑xϾ0.4͒ as the active layer. However, the contact GaN layers absorb a significant fraction of the optical beam thereby reducing the device responsivity and deteriorating UV/visible selectivity.…”

<title>Progress in the fabrication of GaN photocathodes</title>

“…Microchannel plates (MCPs) currently win over CCD-like solid state p-i-n devices made from III-V semi-conductors. The dark current in the p-i-n devices is at least 10 5 times too high (e.g., Parish et al 1999), and there is no clear path to reducing the dark current in these p-i-n devices. The development of photocathodes is the approach most likely to lead to devices for UV space missions over the next 10 years.…”