Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- MBE (2)
- 2DEG (1)
- ALLOYS (1)
- AlInGaN (1)
- CHEMICAL-VAPOR-DEPOSITION; THIN-FILMS; HETEROSTRUCTURES (1)
-
- Complex oxides (1)
- DBR (1)
- DEEP-LEVEL DEFECTS; N-TYPE GAN; DISLOCATION DENSITY; PHASE EPITAXY; ELECTRONIC-STRUCTURES; SILICON; LAYERS (1)
- Detector (1)
- ELECTRIC-FORCE MICROSCOPY; MOLECULAR-BEAM EPITAXY; GAN/ALGAN HETEROSTRUCTURES; GAN(0001)-(1X1) SURFACE; SULFUR PASSIVATION; HEMT PERFORMANCE; ALGAN/GAN HFETS; FERMI-LEVEL; FILMS; RECOMBINATION (1)
- EPITAXIAL LATERAL OVERGROWTH; VAPOR-PHASE EPITAXY; REDUCTION; LAYERS (1)
- Epitaxy (1)
- FILMS; GROWTH (1)
- GaN (1)
- HFETs (1)
- Hot phonons (1)
- InGaN (1)
- LEDs (1)
- MOCVD (1)
- MULTIPLE-QUANTUM WELLS; HEMTS (1)
- MULTIPLE-QUANTUM WELLS; SAPPHIRE; FILMS; REDUCTION; DEFECTS (1)
- Micro-cavity (1)
- Nanonetwork (1)
- ORBIT INTERACTION; RASHBA; FIELD (1)
- P-i-n (1)
- PB(ZR0.3TI0.7)O-3 THIN-FILMS; GAN/SAPPHIRE (1)
- PTO (1)
- PZT (1)
- QUANTUM-WIRE; DEVICES; NOISE (1)
- RTD (1)
- Publication Type
Articles 1 - 18 of 18
Full-Text Articles in Engineering
High Quality Molecular Beam Epitaxy Growth And Characterization Of Lead Titanate Zirconate Based Complex-Oxides, Xing Gu
Theses and Dissertations
Research interest in complex oxides has resurged owing to progress in modern epitaxial techniques. Among such oxides, lead-titanate-based thin films such as PbTiO3 (PTO) and Pb(ZrxTi1−x)O3 (PZT) offer attractive advantages for a wide variety of applications. Moreover, integration between functional oxides with compound semiconductors has the potential to realize multi-functional devices which enjoy the properties from both groups of materials. Ferroelectric materials with a perovskite structure (ABO3) and semiconductors such as GaN with a hexagonal structure, require a careful choice of a bridge layer and suitable epitaxial technique. Molecular beam epitaxy (MBE) …
Electron Mobility In Ingan Channel Heterostructure Field Effect Transistor Structures With Different Barriers, J. Xie, J. H. Leach, X. Ni, M. Wu, R. Shimada, Ü. Özgür, Hadis Morkoç
Electron Mobility In Ingan Channel Heterostructure Field Effect Transistor Structures With Different Barriers, J. Xie, J. H. Leach, X. Ni, M. Wu, R. Shimada, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
InGaN possesses higher electron mobility and velocity than GaN, and therefore is expected to lead to relatively better performances for heterostructure field effect transistors (HFETs). However, the reported mobilities for AlGaN∕InGaNHFETs are lower than GaN channel HFETs. To address this issue, we studied the effect of different barriers on the Hall mobility for InGaN channel HFETs grown by metal organic chemical vapor deposition. Unlike the conventional AlGaN barrier, the AlInN barrier can be grown at the same temperature as the InGaN channel layer, alleviating some of the technological roadblocks. Specifically, this avoids possible degradation of the thin InGaN channel during …
Structural And Electrical Properties Of Pb(Zr,Ti)O3 Films Grown By Molecular Beam Epitaxy, N. Izyumskaya, Vitaliy Avrutin, X. Gu, B. Xiao, Serguei A. Chevtchenko, J-G Yoon, Hadis Morkoç, Lin Zhou, David J. Smith
Structural And Electrical Properties Of Pb(Zr,Ti)O3 Films Grown By Molecular Beam Epitaxy, N. Izyumskaya, Vitaliy Avrutin, X. Gu, B. Xiao, Serguei A. Chevtchenko, J-G Yoon, Hadis Morkoç, Lin Zhou, David J. Smith
Electrical and Computer Engineering Publications
Single-crystal, single-phase Pb(ZrxTi1−x)O3 films (x=0–0.4) were grown on (001)SrTiO3 and SrTiO3:Nb substrates by molecular beam epitaxy. Layer-by-layer growth of thePb(Zr,Ti)O3 films was achieved by using PbTiO3 buffer layers between the SrTiO3substrates and the Pb(Zr,Ti)O3 films. The layers with low Zr content showed high crystallinity with full width at half maximum of ω -rocking curves as low as 4arcmin , whereas increase in Zr concentration led to pronounced angular broadening. The PbZr0.07Ti0.93O3 filmsexhibited remanent polarization as high as 83μC/cm2 , but local areas suffered from nonuniform leakage current.
Epitaxial Growth Of Zro2 On Gan Templates By Oxide Molecular Beam Epitaxy, Xing Gu, Natalia Izyumskaya, Vitaliy Avrutin, Bo Xiao, Hadis Morkoç
Epitaxial Growth Of Zro2 On Gan Templates By Oxide Molecular Beam Epitaxy, Xing Gu, Natalia Izyumskaya, Vitaliy Avrutin, Bo Xiao, Hadis Morkoç
Electrical and Computer Engineering Publications
Molecular beam epitaxial growth of ZrO2 has been achieved on GaN(0001)∕c-Al2O3substrates employing a reactive H2O2 oxygen source. A low temperature buffer followed by in situ annealing and high temperature growth has been employed to attain monoclinic, (100)-oriented ZrO2thin films. The typical full width at half maximum of a 30-nm-thick ZrO2 (100) film rocking curves is 0.4arcdeg and the root-mean-square surface roughness is ∼4Å. ω−2θand pole figure x-ray diffraction patterns confirm the monoclinic structure of ZrO2. Data support an in-plane epitaxial relationship of ZrO2 [010]∥∥GaN[112¯] and ZrO2 [001]∥∥GaN[11¯00]. X-ray diffraction and reflection high-energy electron diffraction analyses reveal in-plane compressive strain, which …
Structural And Electrical Properties Of Pb(Zr,Ti)O3 Grown On (0001) Gan Using A Double Pbtio3∕Pbo Bridge Layer, Bo Xiao, Xing Gu, Natalia Izyumskaya, Vitaliy Avrutin, Jinqiao Xie, Huiyong Liu, Hadis Morkoç
Structural And Electrical Properties Of Pb(Zr,Ti)O3 Grown On (0001) Gan Using A Double Pbtio3∕Pbo Bridge Layer, Bo Xiao, Xing Gu, Natalia Izyumskaya, Vitaliy Avrutin, Jinqiao Xie, Huiyong Liu, Hadis Morkoç
Electrical and Computer Engineering Publications
Pb(Zr0.52Ti0.48)O3 films were deposited by rf magnetron sputtering on silicon-doped GaN(0001)∕c-sapphire with a PbTiO3∕PbO oxide bridge layer grown by molecular beam epitaxy. X-ray diffraction data showed the highly (111)-oriented perovskite phase in lead zirconate titanate(PZT) films with PbTiO3∕PbO bridge layers, compared to the pyrochlore phase grown directly on GaN. The in-plane epitaxial relationships were found from x-ray pole figures to be PZT[112¯]∥∥GaN[11¯00] and PZT[11¯0]∥∥GaN[112¯0]. The polarization-electric field measurements revealed the ferroelectric behavior with remanent polarization of 30–40μC/cm2 and asymmetric hysteresis loops due to the depletion layer formed in GaN under reverse bias which resulted in a high negative coercive electric …
Dielectric Functions And Critical Points Of Pbtio3, Pbzro3, And Pbzr0.57ti0.43o3 Grown On Srtio3 Substrate, T. D. Kang, Hosun Lee, G. Xing, N. Izyumskaya, Vitaliy Avrutin, Bo Xiao, Hadis Morkoç
Dielectric Functions And Critical Points Of Pbtio3, Pbzro3, And Pbzr0.57ti0.43o3 Grown On Srtio3 Substrate, T. D. Kang, Hosun Lee, G. Xing, N. Izyumskaya, Vitaliy Avrutin, Bo Xiao, Hadis Morkoç
Electrical and Computer Engineering Publications
Single crystalline PbTiO3, PbZrO3, and PbZr0.57Ti0.43O3 thin films on SrTiO3 (001) substrates were grown by a combination of molecular beam epitaxy and rf sputtering methods. The authors measured the dielectric functions of the thin films using spectroscopic ellipsometry and determined the interband critical point energies using standard critical point model. They compared the critical point energies to the band structure calculations in the literature. The data suggest that anticrossing behavior occurs between Ea and Eb near Zr=0.17. This phenomenon is attributed to a coupling between X1c and X3c bands caused by intrinsic alloy disorder.
Defect Reduction In Gan Epilayers Grown By Metal-Organic Chemical Vapor Deposition With In Situ Sinx Nanonetwork, Jinqiao Xie, Serguei A. Chevtchenko, Ü. Özgür, Hadis Morkoç
Defect Reduction In Gan Epilayers Grown By Metal-Organic Chemical Vapor Deposition With In Situ Sinx Nanonetwork, Jinqiao Xie, Serguei A. Chevtchenko, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
Line and point defect reductions in thin GaN epilayers with single and double in situ SiNxnanonetworks on sapphire substrates grown by metal-organic chemical vapor deposition were studied by deep-level transient spectroscopy(DLTS), augmented by x-ray diffraction(XRD), and low temperature photoluminescence(PL). All samples measured by DLTS in the temperature range from 80to400K exhibited trap A (peak at ∼325K) with an activation energy of 0.55–0.58eV, and trap B (peak at ∼155K) with an activation energy of 0.21–0.28eV. The concentrations of both traps were much lower for layers with SiNx nanonetwork compared to the reference sample. The lowest concentration was achieved for the sample …
High Electron Mobility In Nearly Lattice-Matched Alinn∕Aln∕Gan Heterostructure Field Effect Transistors, Jinqiao Xie, Xianfeng Ni, Mo Wu, Jacob H. Leach, Ü. Özgür, Hadis Morkoç
High Electron Mobility In Nearly Lattice-Matched Alinn∕Aln∕Gan Heterostructure Field Effect Transistors, Jinqiao Xie, Xianfeng Ni, Mo Wu, Jacob H. Leach, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
High electron mobility was achieved in Al1−xInxN∕AlN∕GaN (x=0.20–0.12)heterostructurefield effect transistors(HFETs) grown by metal-organic chemical vapor deposition. Reduction of In composition from 20% to 12% increased the room temperature equivalent two-dimensional-electron-gas density from 0.90×1013to1.64×1013cm−2 with corresponding electron mobilities of 1600 and 1410cm2/Vs, respectively. The 10Kmobility reached 17600cm2/Vs for the nearly lattice-matched Al0.82In0.18N∕AlN∕GaNheterostructure with a sheet carrier density of 9.6×1012cm−2. For comparison, the AlInN∕GaNheterostructure without the AlN spacer exhibited a high sheet carrier density(2.42×1013cm−2) with low mobility(120cm2/Vs) at room temperature. The high mobility in our samples is in part attributed to ∼1nm AlN spacer which significantly reduces the alloy scattering as well …
Epitaxial Lateral Overgrowth Of (112¯2) Semipolar Gan On (11¯00) M-Plane Sapphire By Metalorganic Chemical Vapor Deposition, X. Ni, Ü. Özgür, A. A. Baski, Hadis Morkoç, Lin Zhou, David J. Smith, C. A. Tran
Epitaxial Lateral Overgrowth Of (112¯2) Semipolar Gan On (11¯00) M-Plane Sapphire By Metalorganic Chemical Vapor Deposition, X. Ni, Ü. Özgür, A. A. Baski, Hadis Morkoç, Lin Zhou, David J. Smith, C. A. Tran
Electrical and Computer Engineering Publications
The authors report the growth of semipolar (112¯2)GaNfilms on nominally on-axis (101¯0) m-plane sapphire substrates using metal organic chemical vapor deposition. High-resolution x-ray diffraction(XRD) results indicate a preferred (112¯2)GaN orientation. Moreover, epitaxial lateral overgrowth (ELO) of GaN was carried out on the (112¯2) oriented GaN templates. When the ELO stripes were aligned along [112¯0]sapphire, the Ga-polar wings were inclined by 32° with respect to the substrate plane with smooth extended nonpolar a-plane GaN surfaces and polar c-plane GaNgrowth fronts. When compared with the template, the on-axis and off-axis XRD rocking curves indicated significant improvement in the crystalline quality by ELO …
Nanostructuring Induced Enhancement Of Radiation Hardness In Gan Epilayers, V. V. Ursaki, I. M. Tiginyanu, O. Volcuic, V. Popa, V. A. Skuratov, Hadis Morkoç
Nanostructuring Induced Enhancement Of Radiation Hardness In Gan Epilayers, V. V. Ursaki, I. M. Tiginyanu, O. Volcuic, V. Popa, V. A. Skuratov, Hadis Morkoç
Electrical and Computer Engineering Publications
The radiation hardness of as-grown and electrochemically nanostructured GaN epilayers against heavy ion irradiation was studied by means of photoluminescence(PL) and resonant Raman scattering (RRS) spectroscopy. A nanostructuring induced enhancement of the GaN radiation hardness by more than one order of magnitude was derived from the PL and RRS analyses. These findings show that electrochemical nanostructuring of GaN layers is a potentially attractive technology for the development of radiation hard devices.
Low Dislocation Densities And Long Carrier Lifetimes In Gan Thin Films Grown On A Sinx Nanonetwork, J. Xie, Ü. Özgür, Y. Fu, X. Ni, Hadis Morkoç, C. K. Inoki, T. S. Kuan, J. V. Foreman, H. O. Everitt
Low Dislocation Densities And Long Carrier Lifetimes In Gan Thin Films Grown On A Sinx Nanonetwork, J. Xie, Ü. Özgür, Y. Fu, X. Ni, Hadis Morkoç, C. K. Inoki, T. S. Kuan, J. V. Foreman, H. O. Everitt
Electrical and Computer Engineering Publications
Significant improvement of structural and optical qualities of GaNthin films on sapphire substrates was achieved by metal organic chemical vapor deposition with in situ SiNxnanonetwork. Transmission electron microscope (TEM) studies revealed that screw- and edge-type dislocations were reduced to 4.4×107 and 1.7×107cm−2, respectively, for a ∼5.5-μm-thick layer. Furthermore, room temperature carrier lifetimes of 2.22 and 2.49ns were measured by time-resolved photoluminescence(TRPL) for samples containing single and double SiNx network layers, respectively, representing a significant improvement over the previous studies. The consistent trends among the TEM,x-ray diffraction, and TRPL measurements suggest that in situ SiNx network reduces line defects effectively as …
Energy Dispersion Relations Of Spin-Split Subbands In A Quantum Wire And Electrostatic Modulation Of Carrier Spin Polarization, Sandipan Pramanik, Supriyo Bandyopadhyay, M. Cahay
Energy Dispersion Relations Of Spin-Split Subbands In A Quantum Wire And Electrostatic Modulation Of Carrier Spin Polarization, Sandipan Pramanik, Supriyo Bandyopadhyay, M. Cahay
Electrical and Computer Engineering Publications
We numerically calculate the energy dispersion relations of the spin-split subbands in a quantum wire subjected to a transverse magnetic field in the presence of Rashba and Dresselhaus spin-orbit interactions. The spin splitting energy at zero wave vector is found to be neither equal to the bare Zeeman splitting nor linear in the magnetic field in any subband. This happens because the expectation value of the spin angular momentum operator varies along the width of the wire, causing a spatial modulation of the spin density. We also show that spin splitting energy is subband dependent and has a complex dependence …
Digital Switch And Femtotesla Magnetic Field Sensor Based On Fano Resonance In A Spin Field Effect Transistor, J. Wan, M. Cahay, S. Bandyopadhyay
Digital Switch And Femtotesla Magnetic Field Sensor Based On Fano Resonance In A Spin Field Effect Transistor, J. Wan, M. Cahay, S. Bandyopadhyay
Electrical and Computer Engineering Publications
We show that a spin field effect transistor, realized with a semiconductor quantum wire channel sandwiched between half-metallic ferromagnetic contacts, can have Fano resonances in the transmission spectrum. These resonances appear because the ferromagnets are half-metallic, so that the Fermi level can be placed above the majority but below the minority spin band. In that case, the majority spins will be propagating, but the minority spins will be evanescent. At low temperatures, the Fano resonances can be exploited to implement a digital binary switch that can be turned on or off with a very small gate voltage swing of few …
Epitaxial Lateral Overgrowth Of A-Plane Gan By Metalorganic Chemical Vapor Deposition, X. Ni, U. Ozgur, H. Morkoç, Z. Liliental-Weber, H. O. Everitt
Epitaxial Lateral Overgrowth Of A-Plane Gan By Metalorganic Chemical Vapor Deposition, X. Ni, U. Ozgur, H. Morkoç, Z. Liliental-Weber, H. O. Everitt
Electrical and Computer Engineering Publications
We report on epitaxial lateral overgrowth (ELO) of (112¯0) a-plane GaN by metalorganic chemical vapor deposition. Different growth rates of Ga- and N-polar wings together with wing tilt create a major obstacle for achieving a smooth, fully coalesced surface in ELOa-plane GaN. To address this issue a two-step growth method was employed to provide a large aspect ratio of height to width in the first growth step followed by enhanced lateral growth in the second by controlling the growth temperature. By this method, the average ratio of Ga- to N-polar wing growth rate has been reduced from 4–6 to 1.5–2, …
Study Of Sinx And Sio2 Passivation Of Gan Surfaces, S. A. Chevtchenko, M. A. Reshchikov, Q. Fan, X. Ni, Y. T. Moon, A. A. Baski, H. Morkoç
Study Of Sinx And Sio2 Passivation Of Gan Surfaces, S. A. Chevtchenko, M. A. Reshchikov, Q. Fan, X. Ni, Y. T. Moon, A. A. Baski, H. Morkoç
Electrical and Computer Engineering Publications
The optical properties of GaN films have been found to be sensitive to SiNx and SiO2 surface passivation. The main effect of such passivation on photoluminescence(PL) data is an increase of the PL intensity for near-band-edge emission. This effect is attributed to the removal of oxygen from the surface of GaN and the subsequent formation of a protective layer during passivation. The increase in PL intensity is more pronounced for samples passivated with SiO2, which demonstrate initially lower PL intensity and a lower equilibrium concentration of free electrons. A nearly constant band bending of approximately 1.0 eV at the surface …
Magnetic Anisotropy And Crystalline Texture In Bao(Fe2o3)(6) Thin Films Deposited On Gan/Al2o3, P. R. Ohodnicki, K. Y. Goh, Y. Hanlumyuang, K. Ramos, M. E. Mchenry, Z. Cai, K. Ziemer, H. Morkoc, N. Biyikli, Z. Chen, C. Vittoria, V. G. Harris
Magnetic Anisotropy And Crystalline Texture In Bao(Fe2o3)(6) Thin Films Deposited On Gan/Al2o3, P. R. Ohodnicki, K. Y. Goh, Y. Hanlumyuang, K. Ramos, M. E. Mchenry, Z. Cai, K. Ziemer, H. Morkoc, N. Biyikli, Z. Chen, C. Vittoria, V. G. Harris
Electrical and Computer Engineering Publications
BaO(Fe2O3)6 (BaM) thin films were deposited by pulsed laser deposition on GaN∕Al2O3 substrates. A pole figure obtained from the (006) reflection indicated that ∼81% of the film volume had the c axis tilted less than 5° from the film normal. A low anisotropy field was inferred from vector coil vibrating sample magnetometer (VVSM) measurements. The reduction in Hafrom literature values and a two-step switching of the easy axis magnetization is postulated to result from interdiffusion and misalignment effects. To alleviate interdiffusion and to improve the c-axis alignment, experiments were repeated with lower deposition temperatures, thinner films, and MgO buffer layers. …
Magnetotransport Properties Of Alxga1-Xn/Aln/Gan Heterostructures Grown On Epitaxial Lateral Overgrown Gan Templates, N. Biyikli, X. Ni, Y. Fu, J. Xie, H. Morkoç, H. Cheng, Ç. Kurdak, I. Vurgaftman, J. R. Meyer
Magnetotransport Properties Of Alxga1-Xn/Aln/Gan Heterostructures Grown On Epitaxial Lateral Overgrown Gan Templates, N. Biyikli, X. Ni, Y. Fu, J. Xie, H. Morkoç, H. Cheng, Ç. Kurdak, I. Vurgaftman, J. R. Meyer
Electrical and Computer Engineering Publications
We studied the low-temperature magnetotransport properties of AlxGa1−xN∕AlN∕GaN heterostructures with a two-dimensional electron gas(2DEG). Structures with different Al compositions were grown by metal-organic vapor-phase epitaxy on three types of templates: conventional undoped GaN, in situ epitaxial lateral overgrown GaN using a SiNx nanomask layer, and ex situe pitaxial lateral overgrown GaN (ELO-GaN) using a stripe-patterned SiO2 mask. All of the samples display Shubnikov–de Haas (SdH) oscillations that confirm the existence of 2DEGs. Field-dependent magnetoresistance and Hall measurements further indicate that the overgrown heterostructures have a parallel conducting layer in addition to the 2DEG. To characterize the parallel channel, we …
Low Dislocation Density Gallium Nitride Templates And Their Device Applications, Jinqiao Xie
Low Dislocation Density Gallium Nitride Templates And Their Device Applications, Jinqiao Xie
Theses and Dissertations
The unique properties, such as large direct bandgap, excellent thermal stability, high μH × ns, of III-nitrides make them ideal candidates for both optoelectronic and high-speed electronic devices. In the past decades, great success has been achieved in commercialization of GaN based light emitting diodes (LEDs) and laser diodes (LDs). However, due to the lack of native substrates, thin films grown on sapphire or SiC substrates have high defect densities that degrade the device performance and reliability. Conventional epitaxy lateral overgrowth (ELO) can reduce dislocation densities down to ∼10-6 cm-2 in the lateral growth area, but requires ex situ photolithography …