Cataloged from PDF version of article.We report p-i-n type InSb-based high-speed photodetectors grown on GaAs substrate. Electrical and optical properties of photodetectors with active areas ranging from 7.06 x 10(-6) cm(2) to 2.25 x 10(-4) cm(2) measured at 77 K and room temperature. Detectors had high zero-bias differential resistances, and the differential resistance area product was 4.5 Omega cm(2). At 77 K, spectral measurements yielded high responsivity between 3 and 5 mum with the cutoff wavelength of 5.33 mum. The maximum responsivity for 80-mum diameter detectors was 1.00x10(5) V/W at 4.35 mum while the detectivity was 3.41x10(9) cm Hz(1/2) /W. High-speed measurements were done at room temperature. An optical parametric oscillator was used to generate picosecond full-width at half-maximum pulses at 2.5 mum with the pump at 780 nm. 30-mum diameter photodetectors yielded 3-dB bandwidth of 8.5 GHz at 2.5 V bias

We have fabricated GaN-based high-speed ultraviolet Schottky photodiodes using indium-tinoxide ͑ITO͒ Schottky contacts. Before device fabrication, the optical transparency of thin ITO films in the visible-blind spectrum was characterized via transmission and reflection measurements. The devices were fabricated on nϪ/nϩ GaN epitaxial layers using a microwave compatible fabrication process. Our ITO Schottky photodiode samples exhibited a maximum quantum efficiency of 47% around 325 nm. Time-based pulse-response measurements were done at 359 nm. The fabricated devices exhibited a rise time of 13 ps and a pulse width of 60 ps.

We report a simple ad hoc method for designing an aperiodic grating structure to quasi-phase match two arbitrary second-order nonlinear processes simultaneously within the same electric-field-poled crystal. This method also allows the relative strength of the two processes to be adjusted freely, thereby enabling maximization of the overall conversion efficiency. We also report an experiment that is based on an aperiodically poled lithium niobate crystal that was designed by use of our method. In this crystal, parametric oscillation and second-harmonic generation are simultaneously phase matched for upconversion of a femtosecond Ti:sapphire laser to 570 nm. This self-doubling optical parametric oscillator provides an experimental verification of our design method.

Design, fabrication, and characterization of high-performance Al x Ga 1 x N-based photodetectors for solar-blind applications are reported. Al x Ga 1 x N heterostructures were designed for Schottky, p-in , 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 reverse bias were measured on p-in samples. The excellent current-voltage (-) characteristics led to a detectivity performance of 4.9 10 14 cmHz 1 2 W 1. The MSM devices exhibited photoconductive gain, while Schottky and p-in samples displayed 0.09 and 0.11 A/W peak responsivity values at 267 and 261 nm, respectively. A visible rejection of 2 10 4 was achieved with Schottky samples. High-speed measurements at 267 nm resulted in fast pulse responses with greater than gigahertz bandwidths. The fastest devices were MSM photodiodes with a maximum 3-dB bandwidth of 5.4 GHz.

Cataloged from PDF version of article.Al0.38Ga0.62N/GaN heterojunction solar-blind Schottky photodetectors with low dark current, high responsivity, and fast pulse\ud response were demonstrated. A five-step microwave compatible fabrication process was utilized to fabricate the devices. The solarblind\ud detectors displayed extremely low dark current values: 30lm diameter devices exhibited leakage current below 3 fA under\ud reverse bias up to 12V. True solar-blind operation was ensured with a sharp cut-off around 266 nm. Peak responsivity of\ud 147mA/W was measured at 256 nm under 20 V reverse bias. A visible rejection more than 4 orders of magnitude was achieved.\ud The thermally-limited detectivity of the devices was calculated as 1.8 · 1013 cmHz1/2W 1\ud . Temporal pulse response measurements\ud of the solar-blind detectors resulted in fast pulses with high 3-dB bandwidths. The best devices had 53 ps pulse-width and 4.1GHz\ud bandwidth. A bandwidth-efficiency product of 2.9GHz was achieved with the AlGaN Schottky photodiodes. (C) 2004 Elsevier Ltd. All rights reserve