Solar-blind avalanche photodiode has gain of 2500

True solar-blind detectors (SBDs) can detect feeble deep-UV (shorter than 290 nm) signals outdoors even under full sunlight, and thus are useful for varied applications such as missile guidance, flame monitoring, and detection of bioagents.

Dec 1st, 2010

True solar-blind detectors (SBDs) can detect feeble deep-UV (shorter than 290 nm) signals outdoors even under full sunlight, and thus are useful for varied applications such as missile guidance, flame monitoring, and detection of bioagents. To compete with photomultiplier tubes, which are large and fragile but are fast and have high internal gain and low dark current, the smaller and more rugged solid-state aluminum gallium nitride (AlGaN) SBDs, much achieve similar performance to PMTs.

A group at Sun Yat-sen University (Guangzhou, China) has fabricated and characterized solar-blind AlGaN avalanche photodiodes (APDs) have a peak responsivity of 79.8 mA/W at 270 nm and zero bias, which is the result of an external quantum efficiency of 37%. The APDs, which have 100 μm diameter active areas, have reached multiplication gains higher than 2500 at a reverse bias of -62 V—the highest value ever for this type of device, say the researchers. The devices, which were grown on 2 in. sapphire wafers using metal-organic chemical-vapor deposition, have a sharp spectral cutoff at 275 nm and a 20 nA dark current at a gain of 10; this dark current is low enough to make these APDs candidates for single-photon detection.

Contact Hao Jiang atstsjiang@mail.sysu.edu.cn.

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