Manijeh Razeghi

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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)
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)
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)
An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor platform was demonstrated for detection of carbon monoxide (CO) and nitrous oxide (N2O). This sensor used a state-of-the art 4.61 μm high power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at 10°C as the excitation source. For(More)
We demonstrate high power, room temperature, single-mode THz emissions based on intracavity difference frequency generation from mid-infrared quantum cascade lasers. Dual active regions both featuring giant nonlinear susceptibilities are used to enhance the THz power and conversion efficiency. The THz frequency is lithographically tuned by integrated(More)
The quantum cascade laser (QCL) is an important laser source in the mid-infrared and terahertz frequency range. The past twenty years have witnessed its tremendous development in power, wall plug efficiency, frequency coverage and tunability, beam quality, as well as various applications based on QCL technology. Nowadays, QCLs can deliver high continuous(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)
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)