High-speed solar-blind AlGaN-based metal–semiconductor–metal photodetectors

Solar-blind AlGaN metal–semiconductor–metal (MSM) photodetectors with fast pulse response have been demonstrated. The devices were fabricated on MOCVD-grown epitaxial Al0.38Ga0.62N layers, using a microwave compatible fabrication process. The photodiode samples exhibited low leakage with dark cur-rent densities below 1 × 10–6 A/cm2 at 40 V reverse bias. Photoconductive gain-assisted photoresponse was observed with a peak responsivity of 1.26 A/W at 264 nm. A visible rejection of ∼3 orders of magni-tude at 350 nm was demonstrated. Temporal high-speed measurements at 267 nm resulted in fast pulse responses with 3-dB bandwidths as high as 5.4 GHz. This corresponds to a record high-speed performan-ce for solar-blind detectors. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Solar-blind photodetectors are important components for applications including missile warning and tracking, engine/flame monitoring, chemical/biological agent detection, and covert space-to-space communication [1, 2]. AlGaN-based solar-blind photodetectors have been extensively studied recently and high-performance solar-blind detection is demonstrated using numerous detector structures [3–9]. Compared with Schottky and p–i–n structures, MSM type of photodiodes (PDs) have the advan