Manijeh Razeghi

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High quality Al 0.2 Ga 0.8 N / GaN superlattices ͑SLs͒ with various ͑GaN͒ well widths ͑1.6 to 6.4 nm͒ have been grown on polar c-plane and nonpolar m-plane freestanding GaN substrates by metal-organic chemical vapor deposition. Atomic force microscopy, high resolution x-ray diffraction, and photoluminescence ͑PL͒ studies of SLs have been carried out to(More)
Research into avalanche photodiodes (APDs) is motivated by the need for high sensitivity ultraviolet (UV) detectors in numerous civilian and military applications. By designing photodetectors to utilize low-noise impact ionization based gain, GaN APDs operating in Geiger mode can deliver gains exceeding 1×10 7. Thus with careful design, it becomes possible(More)
Avalanche p-in photodiodes were fabricated on AlN templates for back illumination. Structures with different intrinsic layer thicknesses were tested. A critical electric field of 2.73 MV/ cm was estimated from the variation of the breakdown voltage with thickness. From the device response under back and front illumination and the consequent selective(More)
M-plane GaN avalanche p-in photodiodes on low dislocation density freestanding m-plane GaN substrates were realized using metal-organic chemical vapor deposition. High quality homoepitaxial m-plane GaN layers were developed; the root-mean-square surface roughness was less than 1 Å and the full-width-at-half-maximum value of the x-ray rocking curve for ͑101(More)
Hybrid green light-emitting diodes ͑LEDs͒ comprised of n-ZnO/ ͑InGaN/ GaN͒ multi-quantum-wells/p-GaN were grown on semi-insulating AlN/sapphire using pulsed laser deposition for the n-ZnO and metal organic chemical vapor deposition for the other layers. X-ray diffraction revealed that high crystallographic quality was preserved after the n-ZnO growth. LEDs(More)
(Invited Talk) SUMMARY III-Nitride material system (AlGaInN) possesses unique optical, electrical and structural properties such as a wide tunable direct bandgap, large longitudinal optical phonon energy, inherit fast carrier dynamics; good carrier transport properties, high breakdown fields; and high robustness and chemical stability. Thanks to these(More)
AlGaN/GaN resonant tunneling diodes ͑RTDs͒, consisting of 20% ͑10%͒ aluminum-content in double-barrier ͑DB͒ active layer, were grown by metal-organic chemical vapor deposition on freestanding polar ͑c-plane͒ and nonpolar ͑m-plane͒ GaN substrates. RTDs were fabricated into 35-␮m-diameter devices for electrical characterization. Lower aluminum content in the(More)
High quality ␦-doped p-GaN is used as a means of improving the performance of back-illuminated GaN avalanche photodiodes ͑APDs͒. Devices with ␦-doped p-GaN show consistently lower leakage current and lower breakdown voltage than those with bulk p-GaN. APDs with ␦-doped p-GaN also achieve a maximum multiplication gain of 5.1ϫ 10 4 , more than 50 times higher(More)
AlN/GaN double-barrier resonant tunneling diodes ͑RTDs͒ were grown by metal-organic chemical vapor deposition on sapphire. RTDs were fabricated via standard processing steps. RTDs demonstrate a clear negative differential resistance ͑NDR͒ at room temperature ͑RT͒. The NDR was observed around 4.7 V with a peak current density of 59 kA/ cm 2 and a(More)