Avalanche multiplication in AlGaN based solar-blind photodetectors

Abstract

Avalanche multiplication has been observed in solar-blind AlGaN-based p-i-n photodiodes. Upon ultraviolet illumination, the optical gain shows a soft breakdown starting at relatively low electric fields, eventually saturating without showing a Geiger mode breakdown. The devices achieve a maximum optical gain of 700 at a reverse bias of 60 V. By modeling the device, it is found that this corresponds to an electric-field strength of 1.7MV∕cm.

AlGaN solar-blind avalanche photodiodes with high multiplication gain

“…It is the highest multiplication gain ever reported for the AlGaN-based solar-blind APDs. The above result is in contrast with the result reported before, 9 which shows a soft avalanche breakdown where the gain increases exponentially over a fivefold increase in the voltage. Dark current at a multiplication gain of 10 is only about 20 nA, indicating that these devices are potential candidate for single-photon detection application.…”

AlxGa1–xN‐based avalanche photodiodes with high reproducible avalanche gain

“…The gain measurements showed an exponential dependence on voltage, in which we infer from this result that the photoconductive gain is not a possible gain mechanism in our devices. We know that the photoconductive gain increases linearly with voltage [19,22]. Therefore, we conclude that the gain in these devices result from the avalanche multiplication of the photogenerated carriers in the active region of the devices.…”

“…There have been several theoretical research work that examined the avalanche effect in GaN and AlGaN-based structures [9][10][11]. Experimental work on both GaN [12][13][14][15][16][17][18] and AlGaN-based [4,19,20] avalanche photodiodes (APDs) were also reported. However, reproducible high-gain in AlGaN-based APDs is still a major limitation.…”

(Invited) Enhancing the Deep Ultraviolet Performance of 4H-SiC Based Photodiodes

“…While semiconductor avalanche photodiodes (APDs) can be more compact, lower cost and more rugged than the commonly used photomultiplier tubes (PMTs), commercially available devices such as silicon (Si) single photon counting APDs have poor DUV single photon detection efficiency. Aluminum gallium nitride (Al x Ga 1-x N) photodetectors can take advantage of a sharp and tunable direct band gap to achieve high external quantum efficiency (2,3), and avalanche multiplication in Al x Ga 1-x N based p-i-n diodes has been reported (2,4,5). However, this approach is limited by the difficulty in doping high AlN mole fraction alloys p-type, and a very large breakdown electric field for high AlN mole fraction that implies higher voltage operation and greater susceptibility to dark current associated with defects in the material.…”