Comparison of the Incorporation of Various Transition Metals into GaN by MOCVD

2006 ◽  
Vol 955 ◽  
Author(s):  
Matthew H Kane ◽  
William Fenwick ◽  
Nola Li ◽  
Shalini Gupta ◽  
Eun Hyun Park ◽  
...  
Keyword(s):  
Transition Metals ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Magnetic Hysteresis ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Growth Conditions ◽  
Shallow Donor ◽  
Organic Chemical ◽  
Secondary Phases

ABSTRACTThe incorporation of transition metals in GaN has long been of interest in spintronics due to theoretical predictions of room temperature ferromagnetism in these materials. However, the mechanism of the observed ferromagnetism of the nitride-based DMS is still controversial, and may originate from a carrier-mediated, defect-related or nanoscale clustering mechanism. In this work, we present a comparative study of the incorporation of various transition metals and their effect on the optical, structural, and magnetic properties of GaN. Metal-organic chemical vapor deposition (MOCVD) has been employed to produce epitaxial films of varying thickness and manganese and iron doping using bis-cyclopentyldienyl(magnanese,iron) as the transition metal sources. High-resolution X-ray diffraction reveals no secondary phases under optimized growth conditions. Magnetic hysteresis is observed at room temperature in both GaMnN and GaFeN, though the strength of the magnetic ordering is roughly an order of magnitude weaker in the Fe-alloyed samples. Increasing Mn concentrations significantly affect long-range lattice ordering, and the observation of local vibrational modes (LVMs) supports the formation of nitrogen vacancies, even under optimized MOCVD growth conditions. Such vacancies form shallow donor complexes and thus contribute to self-compensation. A disorder-induced mode at 300 cm−1 and a LVM due to vacancies at 669 cm-1 were revealed by Raman spectroscopy.

THE GROWTH AND CHARACTERIZATION OF ROOM TEMPERATURE FERROMAGNETIC WIDEBAND-GAP MATERIALS FOR SPINTRONIC APPLICATIONS

2006 ◽  
Vol 16 (02) ◽  
pp. 515-543
Author(s):  
MATTHEW H. KANE ◽  
MARTIN STRASSBURG ◽  
WILLIAM E. FENWICK ◽  
ALI ASGHAR ◽  
IAN T. FERGUSON
Keyword(s):  
Room Temperature ◽  
Magnetic Semiconductors ◽  
Room Temperature Ferromagnetism ◽  
Dilute Magnetic Semiconductors ◽  
Chemical Vapor ◽  
Wide Bandgap ◽  
Organic Chemical ◽  
Ferromagnetic Behavior ◽  
Spintronic Devices

Wide-bandgap dilute magnetic semiconductors (DMS), such as transition-metal doped ZnO and GaN , have gained attention for use in spintronic devices because of predictions and experimental reports of room temperature ferromagnetism which may enable their use in spintronic devices. However, there has been some debate over the source of ferromagnetism in these materials. This paper focuses on the high quality growth of wide bandgap DMS, and the characterization of Zn 1-x Mn x O produced by melt-growth techniques and Ga 1-x Mn x N grown by metal organic chemical vapor deposition (MOCVD). High resolution X-ray diffraction results revealed no second phases in either the ZnO crystals or the GaN films. Undoped as-grown, bulk crystals of Zn 1-x Mn x O and Zn 1-x Co x O crystals are shown to be paramagnetic at all temperatures. In contrast, the Ga 1-x Mn x N films showed ferromagnetic behavior at room temperature under optimum growth conditions. Experimental identification of the Mn ion charge state and the presence of bands in the bandgap of GaN are investigated by optical spectroscopy and electron spin paramagnetic resonance (EPR). It is shown that the broadening of states in the Mn 3d shell scaled with Mn concentration, and that optical transitions due to this band correlated with the strong ferromagnetism in these samples. However, this band disappeared with an increase in free electron concentration provided by either annealing or doping. Raman studies of Ga 1-x Mn x N revealed two predominant Mn -related modes featured with increasing concentration, a broad disorder related structure at 300cm-1 and a sharper peak at 669cm-1 This works show that the development of practical ferromagnetic wide bandgap DMS materials for spintronic applications will require both the lattice site introduction of Mn as well as careful control of the background defect concentration to optimize these materials.

Growth of GaAs/AlGaAs Quantum Dots Using Self-Organized InP Stressors

1995 ◽  
Vol 417 ◽  
Author(s):  
M. C. Hanna ◽  
Z. H. Lu ◽  
A. F. Cahill ◽  
M. J. Heben ◽  
A. J. Nozik
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Organic Chemical ◽  
Near Surface ◽  
Self Organized ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

AbstractGaAs quantum dots were formed in a near surface quantum well (QW) by producing lateral confinement with self-organized InP stressors grown in situ by metal organic chemical vapor deposition (MOCVD). We report here the influence of growth conditions on InP island formation on AlGaAs/GaAs single QW structures and also the influence of the QW structure on the optical properties of the GaAs quantum dots. We observe strong photoluminscence up to room temperature from the strain-induced quantum dots with energy redshifts of 70 meV below the QW peak.

Evidence of Carrier Mediated Ferromagnetism in GaN:Mn/GaN:Mg Heterostructures

2004 ◽  
Vol 831 ◽  
Author(s):  
F. Erdem Arkun ◽  
Mason J. Reed ◽  
Erkan Acar Berkman ◽  
Nadia A. El-Masry ◽  
John M. Zavada ◽  
...  
Keyword(s):  
Fermi Level ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Room Temperature Ferromagnetism ◽  
Dilute Magnetic Semiconductors ◽  
Organic Chemical ◽  
Material System ◽  
Secondary Phases ◽  
Fermi Level Position ◽  
Carrier Transfer

ABSTRACTDilute Magnetic Semiconductors (DMS's) posses a strong potential to make use of the spin of carriers in spintronic devices. Experimental results and theoretical calculations predict that GaN:Mn is a potential semiconductor material for spintronic device applications. The dependence of the room temperature ferromagnetic properties of GaN:Mn/GaN:Mg double heterostructures (DHS) on the Fermi level position in the crystal is demonstrated. Several GaN:Mn/GaN:Mg DHS are grown by metal organic chemical vapor deposition on sapphire. It is shown that initially paramagnetic films can be rendered ferromagnetic by facilitating carrier transfer through the GaN:Mn/GaN:Mg interface. Additionally, it is demonstrated that ferromagnetism depends on the thickness of the GaN:Mn and GaN:Mg layers. The carrier transfer process essentially changes the Fermi level position in the crystal. By choosing the right thicknesses for GaN:Mn and GaN:Mg an optimum DHS that exhibits room temperature ferromagnetism is grown. An identical structure, with the exception of insertion of an AlGaN barrier in order to obstruct the carrier transfer at the interface, results in paramagnetic films for AlGaN barriers thicker than 25nm. These results are explained based on the change in the occupancy of the 3d-Mn impurity band, and indicate that carrier mediation is the possible mechanism for the ferromagnetism observed in the MOCVD grown GaN:Mn material system. This is the first evidence that this material system responds to electronic perturbations, hence ferromagnetism observed is not due to secondary phases or spin glass behavior.

TEM study of very thin InGaAsP layers grown by liquid-phase epitaxy

1990 ◽  
Vol 48 (4) ◽  
pp. 672-673
Author(s):  
N.A. Bert ◽  
A.O. Kosogov
Keyword(s):  
Liquid Phase ◽  
Liquid Phase Epitaxy ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Dark Field ◽  
Organic Chemical ◽  
Simple Liquid ◽  
Cross Sectional ◽  
Conventional Procedure ◽  
Double Heterostructures

The very thin (<100 Å) InGaAsP layers were grown not only by molecular beam epitaxy and metal-organic chemical vapor deposition but recently also by simple liquid phase epitaxy (LPE) technique. Characterization of their thickness, interfase abruptness and lattice defects is important and requires TEM methods to be used.The samples were InGaAsP/InGaP double heterostructures grown on (111)A GaAs substrate. The exact growth conditions are described in Ref.1. The salient points are that the quarternary layers were being grown at 750°C during a fast movement of substrate and a convection caused in the melt by that movement was eliminated. TEM cross-section specimens were prepared by means of conventional procedure. The studies were conducted in EM 420T and JEM 4000EX instruments.The (200) dark-field cross-sectional imaging is the most appropriate TEM technique to distinguish between individual layers in 111-v semiconductor heterostructures.

Observations on the Growth of YBa2Cu3O7 Thin Films at Very High Laser Fluences

1995 ◽  
Vol 388 ◽  
Author(s):  
Rand R. Biggers. ◽  
M. Grant Norton ◽  
I. Maartense ◽  
T.L. Peterson ◽  
E. K. Moser ◽  
...  
Keyword(s):  
Thin Films ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Organic Chemical ◽  
High Fluences ◽  
Laser Fluences ◽  
High Laser ◽  
High Laser Fluences ◽  
Very High

AbstractThe pulsed-laser deposition (PLD) technique utilizes one of the most energetic beams available to form thin films of the superconducting oxide YBa2Cu3O7 (YBCO). IN this study we examine the growth of YBCO at very high laser fluences (25 to 40 J/cm2); a more typical fluence for PLD would be nearer to 3 J/cm2. the use of high fluences leads to unique film microstructures which, in some cases, appear to be related to the correspondingly higher moveabilities of the adatoms. Films grown on vicinal substrates, using high laser fluences, exhibited well-defined elongated granular morphologies (with excellent transition temperature, Tc, and critical current density, Jc). Films grown on vicinal substrates using off-axis magnetron sputtering, plasma-enhanced metal organic chemical vapor deposition (PE-MOCVD), or PLD at more typical laser fluences showed some similar morphologies, but less well-defined. Under certain growth conditions, using high laser fluences with (001) oriented substrates, the YBCO films can exhibit a mixture of a- and c-axis growth where both crystallographic orientations nucleate on the substrate surface at the same time, and grow in concert. the ratio of a-axis oriented to c-axis oriented grains is strongly affected by the pulse repetition rate of the laser.

Molecule-Based Magnets—An Overview

MRS Bulletin ◽  
2000 ◽  
Vol 25 (11) ◽  
pp. 21-30 ◽  
Author(s):  
Joel S. Miller ◽  
Arthur J. Epstein
Keyword(s):  
Low Temperature ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Low Density ◽  
Materials Properties ◽  
The Common ◽  
New Processing ◽  
Very High

Molecule-based magnets are a broad, emerging class of magnetic materials that expand the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal and rare-earth-based magnets can be found in molecule-based magnets. Although discovered less than two decades ago, magnets with ordering temperatures exceeding room temperature, very high (∼27.0 kOe or 2.16 MA/m) and very low (several Oe or less) coercivities, and substantial remanent and saturation magnetizations have been achieved. In addition, exotic phenomena including photoresponsiveness have been reported. The advent of molecule-based magnets offers new processing opportunities. For example, thin-film magnets can be prepared by means of low-temperature chemical vapor deposition and electrodeposition methods.

GaN-based blue laser diode with 6.0 W of output power under continuous-wave operation at room temperature

2021 ◽  
Vol 42 (11) ◽  
pp. 112801
Author(s):  
Feng Liang ◽  
Degang Zhao ◽  
Zongshun Liu ◽  
Ping Chen ◽  
Jing Yang ◽  
...  
Keyword(s):  
Laser Diode ◽  
Room Temperature ◽  
Continuous Wave ◽  
Chemical Vapor ◽  
Threshold Current ◽  
Stimulated Emission ◽  
Blue Laser ◽  
Organic Chemical ◽  
Blue Laser Diode ◽  
Continuous Wave Operation

Abstract In this work, we reported the room-temperature continuous-wave operation of 6.0 W GaN-based blue laser diode (LD), and its stimulated emission wavelength is around 442 nm. The GaN-based high power blue LD is grown on a c-plane GaN substrate by metal organic chemical vapor deposition (MOCVD), and the width and length of the ridge waveguide structure are 30 and 1200 μm, respectively. The threshold current is about 400 mA, and corresponding threshold current density is 1.1 kA/cm2.

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