Browsing by Subject "Photomultipliers"
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Item Open Access High-performance solar-blind AlGaN photodetectors(SPIE, 2005) Özbay, Ekmel; Tut, Turgut; Bıyıklı, N.Design, fabrication, and characterization of high-performance Al xGa1-xN-based photodetectors for solar-blind applications are reported. AlxGa1-xN heterostructures were designed for Schottky, p-i-n, and metal-semiconductor-metal (MSM) photodiodes. The solar-blind photodiode samples were fabricated using a microwave compatible fabrication process. The resulting devices exhibited extremely low dark currents. Below 3 fA leakage currents at 6 V and 12 V reverse bias were measured on p-i-n and Schottky photodiode samples respectively. The excellent current-voltage (I-V) characteristics led to a detectivity performance of 4.9×1014 cmHz1/2W-1. The MSM devices exhibited photoconductive gain, while Schottky and p-i-n samples displayed 0.15 A/W and 0.11 A/W peak responsivity values at 267 nm and 261 nm respectively. All samples displayed true solar-blind response with cut-off wavelengths smaller than 280 nm. A visible rejection of 4×104 was achieved with Schottky detector samples. High speed measurements at 267 nm resulted in fast pulse responses with >GHz bandwidths. The fastest devices were MSM photodiodes with a maximum 3-dB bandwidth of 5.4 GHz.Item Open Access High-performance solar-blind AlGaN photodetectors(IEEE, 2004) Özbay, Ekmel; Bıyıklı, Necmi; Kimukin, İbrahim; Tut, Turgut; Kartaloğlu, Tolga; Aytür, OrhanHigh-performance aluminum gallium nitride (AlGaN)-based solar-blind (SB) photodetectors were demonstrated using different device structures. The Al x-Ga1-xN layers structure were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire structures. n+ and p+ ohmic contacts on GaN were formed with non-annealed titanium (Ti)/aluminum (Al) and nickel (Ni)/ gold (Au) alloys. Spectral UV photoresponse measurements confirmed the solar-blind response of the devices.Item Open Access Strong enhancement of spontaneous emission in hydrogenated amorphous silicon nitride coupled-microcavity structures(IEEE, 2001) Bayındır, Mehmet; Tanrıseven, Selim; Aydınlı, Atilla; Özbay, EkmelThe modification of spontaneous emission from the hydrogenated amorphous silicon nitride layers in a coupled-microcavity (CMC) structure was investigated. The CMC structure was composed of alternating silicon-oxide and silicon-nitride multilayers. The results showed that the strong enhancement of spontaneous emisssion can be achieved throughout the cavity band.