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Dive into the research topics where Mikhail Gaevski is active.

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Featured researches published by Mikhail Gaevski.


Applied Physics Letters | 2002

Crack-free thick AlGaN grown on sapphire using AlN/AlGaN superlattices for strain management

J. P. Zhang; H. M. Wang; Mikhail Gaevski; C. Q. Chen; Q. Fareed; J. Yang; Grigory Simin; M. Asif Khan

We report on an AlN/AlGaN superlattice approach to grow high-Al-content thick n+-AlGaN layers over c-plane sapphire substrates. Insertion of a set of AlN/AlGaN superlattices is shown to significantly reduce the biaxial tensile strain, thereby resulting in 3-μm-thick, crack-free Al0.2Ga0.8N layers. These high-quality, low-sheet-resistive layers are of key importance to avoid current crowding in quaternary AlInGaN multiple-quantum-well deep-ultraviolet light-emitting diodes over sapphire substrates.


Applied Physics Letters | 2004

Anisotropic structural characteristics of (112̄0) GaN templates and coalesced epitaxial lateral overgrown films deposited on (101̄2) sapphire

H. M. Wang; C. Q. Chen; Zheng Gong; Jianping Zhang; Mikhail Gaevski; Ming Su; Jinwei Yang; M. Asif Khan

a-plane GaN templates and coalesced epitaxial lateral overgrown (ELOG) films on r-plane sapphire substrates were investigated by x-ray diffraction (XRD). The a-plane GaN templates were found to have [0001]-oriented stripe-features, which is related to anisotropic mosaicity. For the mosaic blocks, the mosaicity reached the largest and the smallest values along the [1100] and the [0001] directions. The ELOG procedure with the SiO2 mask stripes perpendicular to the [0001] direction limits the preferable growth along this direction, and thereby enhances the [1100] growth. This leads to large-area, featureless, a-plane GaN films for which the wing tilt and not the fine mosaic block size becomes the major XRD line-broadening mechanism.


Applied Physics Letters | 2002

Self-heating effects at high pump currents in deep ultraviolet light-emitting diodes at 324 nm

A. Chitnis; J. Sun; R. Pachipulusu; S. Wu; Mikhail Gaevski; Vinod Adivarahan; J. P. Zhang; M. Asif Khan; Andrei Sarua; Martin Kuball

We present a detailed high-pump-current study of self-heating effects in ultraviolet light-emitting diodes (LEDs) grown on sapphire. For deep ultraviolet LEDs on sapphire, our results establish self-heating to be a primary cause of premature power saturation under dc pumping. Even the flip-chip packaged devices undergo a steady-state temperature rise to about 70 °C at a dc pump current of only 50 mA (at 8 V) resulting in a significant decrease in LED output. Temperature rise values estimated from peak emission wavelength shifts and from micro-Raman mapping of the active devices were in good agreement.


Applied Physics Letters | 2002

Polarization effects in photoluminescence of C- and M-plane GaN/AlGaN multiple quantum wells

E. Kuokstis; C. Q. Chen; Mikhail Gaevski; Wenhong Sun; J. Yang; Grigory Simin; M. Asif Khan; H. P. Maruska; David W. Hill; M. M. C. Chou; J. J. Gallagher; Bruce H. T. Chai

Polarization effects have been studied in GaN/AlGaN multiple quantum wells (MQWs) with different c-axis orientation by means of excitation-dependent photoluminescence (PL) analysis. Quantum structures were grown on [0001]-oriented sapphire substrates (C plane) and single-crystalline [1100]-oriented freestanding GaN (M plane) using the metalorganic chemical vapor deposition technique. Strong PL spectrum line blueshifts (up to 140 meV) which are correlated with the excitation intensity have been obtained for C-plane MQWs, whereas no shift has been observed for M-plane MQWs. Theoretical calculations and comparison with the PL data confirm that the built-in electric field for C-plane structures is much stronger than the field present for M-plane MQWs. In the former case, the excitation-induced blueshift of the PL line is due to the screening of the built-in electric field by photoinjected carriers, which is consistent with the field strength of 1.23 MV/cm in the absence of excitation.


Applied Physics Letters | 2002

GaN homoepitaxy on freestanding (11̄00) oriented GaN substrates

C. Q. Chen; Mikhail Gaevski; Wenhong Sun; E. Kuokstis; J. P. Zhang; R. S. Q. Fareed; H. M. Wang; J. Yang; Grigory Simin; M. A. Khan; H. P. Maruska; David W. Hill; Mitch M.C. Chou; Bruce H. T. Chai

We report homoepitaxial GaN growth on freestanding (1100) oriented (M-plane GaN) substrates using low-pressure metalorganic chemical vapor deposition. Scanning electron microscopy, atomic-force microscopy, and photoluminescence were used to study the influence of growth conditions such as the V/III molar ratio and temperature on the surface morphology and optical properties of the epilayers. Optimized growth conditions led to high quality (1100) oriented GaN epilayers with a smooth surface morphology and strong band-edge emission. These layers also exhibited strong room temperature stimulated emission under high intensity pulsed optical pumping. Since for III-N materials the (1100) crystal orientation is free from piezoelectric or spontaneous polarization electric fields, our work forms the basis for developing high performance III-N optoelectronic devices.


IEEE Electron Device Letters | 2003

Submicron gate Si 3 N 4 /AlGaN/GaN-metal-insulator-semiconductor heterostructure field-effect transistors

Vinod Adivarahan; Mikhail Gaevski; Wenhong Sun; H. Fatima; A. Koudymov; Salih Saygi; Grigory Simin; J. Yang; M. A. Khan; A. Tarakji; M. S. Shur; R. Gaska

We present the characteristics of a quarter-micron gate metal-insulator-semiconductor heterostructure field-effect transistor (MISHFET) with Si/sub 3/N/sub 4/ film as a gate insulator. A detailed comparison of the MISHFET and an identical geometry HFET shows them to have the same radio frequency (RF) power gain and cut-off frequency, while the MISHFET has much lower gate-leakage currents and higher RF powers at operating frequencies as high as 26 GHz. The MISHFET gate-leakage currents are well below 100 pA at gate bias values from -10 V to +8 V. At zero gate bias, the drain saturation current is about 0.9 A/mm and it increases to 1.2 A/mm at +8 V gate bias. The output RF power of around 6 W/mm at 40 drain bias was found to be frequency independent in the range of 2 to 26 GHz. This power is 3 dB higher than that from HFET of the same geometry. The intrinsic cutoff frequency is /spl sim/63 GHz for both the HFET and the MISHFET. This corresponds to an average effective electron velocity in the MISHFET channel of 9.9/spl times/10/sup 6/ cm/s. The knee voltage and current saturation mechanisms in submicron MISHFETs and heterostructure field-effect transistors (HFET) are also discussed.


Japanese Journal of Applied Physics | 2003

A New Selective Area Lateral Epitaxy Approach for Depositing a-Plane GaN over r-Plane Sapphire

C. Q. Chen; Jianping Zhang; Jinwei Yang; Vinod Adivarahan; S. Rai; S. Wu; H. M. Wang; Wenhong Sun; Ming Su; Zheng Gong; E. Kuokstis; Mikhail Gaevski; Muhammad Asif Khan

We report a new epitaxy procedure for growing extremely low defect density a-plane GaN films over r-plane sapphire. By combining selective area growth through a SiO2 mask opening to produce high height to width aspect ratio a-plane GaN pillars and lateral epitaxy from their c-plane facets, we obtained fully coalesced a-plane GaN films. The excellent structural, optical and electrical characteristics of these selective area lateral epitaxy (SALE) deposited films make them ideal for high efficiency III-N electronic and optoelectronic devices.


Applied Physics Letters | 2006

Pulsed lateral epitaxial overgrowth of aluminum nitride on sapphire substrates

Z. Chen; R. S. Qhalid Fareed; Mikhail Gaevski; Vinod Adivarahan; J. Yang; Asif Khan; J. Mei; F. A. Ponce

The authors report on pulsed lateral epitaxial overgrowth of aluminum nitride films on basal plane sapphire substrates. This approach, at temperatures in excess of 1150°C, enhanced the adatom migration, thereby significantly increasing the lateral growth rates. This enabled a full coalescence in wing regions as wide as 4–10μm. Atomic force microscopy and cross-section transmission electron microscopy were used to establish the reduction of threading dislocations in the lateral growth. Cross-sectional monochromatic cathodoluminescence and photoluminescence measurements confirmed the improved optical properties of the laterally overgrown aluminum nitride films.The authors report on pulsed lateral epitaxial overgrowth of aluminum nitride films on basal plane sapphire substrates. This approach, at temperatures in excess of 1150°C, enhanced the adatom migration, thereby significantly increasing the lateral growth rates. This enabled a full coalescence in wing regions as wide as 4–10μm. Atomic force microscopy and cross-section transmission electron microscopy were used to establish the reduction of threading dislocations in the lateral growth. Cross-sectional monochromatic cathodoluminescence and photoluminescence measurements confirmed the improved optical properties of the laterally overgrown aluminum nitride films.


Japanese Journal of Applied Physics | 2003

Lateral Epitaxial Overgrowth of Fully Coalesced A-Plane GaN on R-Plane Sapphire

C. Q. Chen; Jinwei Yang; H. M. Wang; Jianping Zhang; Vinod Adivarahan; Mikhail Gaevski; E. Kuokstis; Zheng Gong; Ming Su; Muhammad Asif Khan

Fully coalesced epitaxial laterally overgrown a-plane GaN films were characterized for their structural and optical quality. The films had a very smooth surface with a root mean square roughness as low as 4.6 ? for a 5 ?m ? 5 ?m atomic force microscope scan area. They exhibited a wing tilt of only 0.27? and optically pumped stimulated emission, which establish their high structural and optical quality. These non-polar films are ideal for fabricating high-efficiency optoelectronic and electronic devices.


Japanese Journal of Applied Physics | 2006

Room-Temperature Stimulated Emission from AlN at 214 nm

M. Shatalov; Mikhail Gaevski; Vinod Adivarahan; Asif Khan

We report the first ever room temperature (RT) stimulated emission at 214 nm using high quality AlN layers that were grown over patterned sapphire substrates by pulsed lateral epitaxial overgrowth (PLOG) process. The PLOG process yielded fully coalesced layers with total thicknesses in excess of 10 µm resulting in a reduction in the threading dislocation density by several orders. The stimulated emission was achieved at 214 nm under pulsed optical pumping at RT. The RT threshold optical power density was approximately 9 MW/cm2 and the stimulated edge-emission signal was strongly polarized with E∥c.

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Vinod Adivarahan

University of South Carolina

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Grigory Simin

University of South Carolina

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M. Asif Khan

University of South Carolina

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M. Shatalov

University of South Carolina

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Wenhong Sun

University of South Carolina

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C. Q. Chen

University of South Carolina

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J. Yang

University of South Carolina

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R. Gaska

Rensselaer Polytechnic Institute

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E. Kuokstis

University of South Carolina

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Zheng Gong

University of South Carolina

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