Spectroscopic Investigation of Traps Producing Current Collapse In AlGaN/GaN Hemt Structures

2001 ◽  
Vol 680 ◽  
Author(s):  
P.B. Klein ◽  
S.C. Binari ◽  
K. Ikossi ◽  
A.E. Wickenden ◽  
D.D. Koleske ◽  
...  
Keyword(s):  
Spectroscopic Investigation ◽  
The Other ◽  
Buffer Layers ◽  
Structural Defects ◽  
High Resistivity ◽  
Lower Growth ◽  
Gan Hemt ◽  
Current Collapse ◽  
Trapping Centers ◽  
Gan Buffer Layer

ABSTRACTPhotoionization spectroscopy (PS) measurements, previously carried out for the GaN MESFET, have been extended to the more complicated AlGaN/GaN HEMT structures. In all cases, the spectra revealed that the same two traps causing current collapse in the high resistivity (HR) GaN buffer layer of the MESFET were also responsible for current collapse in the HEMT structures. The HR buffer layers supporting the HEMT structures were prepared by MOVPE at varying growth pressures, in order to vary the incorporation of deep trapping centers. Lower growth pressures were observed to correlate with more severe current collapse and with an enhanced incorporation of carbon. Detailed analysis of the PS data suggests that one of the two responsible traps is related to carbon, while the other may be associated with structural defects in the material.

Nucleation and Heterointerface Structure of InAs Epilayers Grown on InP Substrates

1992 ◽  
Vol 280 ◽  
Author(s):  
K. S. Chandra Sekhar ◽  
A. K. Ballal ◽  
L. Salamanca-Riba ◽  
D. L. Partin
Keyword(s):  
Surface Morphology ◽  
Electronic Properties ◽  
Growth Temperature ◽  
High Speed ◽  
Interface Roughness ◽  
Structural Defects ◽  
Lower Growth ◽  
Substrate Interface ◽  
Film Substrate ◽  
Inp Substrates

ABSTRACTHeteroepitaxial growth of indium arsenide films on indium phosphide substrates is being actively pursued since the electronic properties of these films make them promising materials for optoelectronic and other high speed devices. The various structural aspects of the film that affect their electronic properties are structural defects like dislocations, film-substrate interface roughness and chemical inhomogeneities. In InAs films, electrons accumulate at the film-air interface, making surface morphology an important factor that decides the electronic properties. The InAs films used in this study were grown on InP substrates by metal organic vapor deposition, at different temperatures. A higher growth temperature not only resulted in poor surface morphology of the film, but also created a rough film-substrate interface. However, at all deposition temperatures, the film-substrate interfaces are sharp. At lower growth temperature, the interfaces were flat. Films grown at lower temperatures had good surface morphology and a flat and shaip heterointerface.

The Influence of Growth Temperature on Oxygen Concentration in GaN Buffer Layer

2008 ◽  
Vol 1068 ◽  
Author(s):  
Ewa Dumiszewska ◽  
Wlodek Strupinski ◽  
Piotr Caban ◽  
Marek Wesolowski ◽  
Dariusz Lenkiewicz ◽  
...  
Keyword(s):  
High Temperature ◽  
Buffer Layer ◽  
Oxygen Concentration ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Buffer Layers ◽  
Crystalline Quality ◽  
Temperature Growth ◽  
Gan Buffer Layer

ABSTRACTThe influence of growth temperature on oxygen incorporation into GaN epitaxial layers was studied. GaN layers deposited at low temperatures were characterized by much higher oxygen concentration than those deposited at high temperature typically used for epitaxial growth. GaN buffer layers (HT GaN) about 1 μm thick were deposited on GaN nucleation layers (NL) with various thicknesses. The influence of NL thickness on crystalline quality and oxygen concentration of HT GaN layers were studied using RBS and SIMS. With increasing thickness of NL the crystalline quality of GaN buffer layers deteriorates and the oxygen concentration increases. It was observed that oxygen atoms incorporated at low temperature in NL diffuse into GaN buffer layer during high temperature growth as a consequence GaN NL is the source for unintentional oxygen doping.

Defects in HgCdTe grown by molecular beam epitaxy on GaAs substrates

2012 ◽  
Vol 20 (4) ◽  
Author(s):  
I. Izhnin ◽  
A. Izhnin ◽  
H. Savytskyy ◽  
O. Fitsych ◽  
N. Mikhailov ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Structural Defects ◽  
Donor Concentration ◽  
Ion Milling ◽  
Electrical And Optical Properties ◽  
Gaas Substrates ◽  
Cdte Buffer

AbstractThe Hall effect and photoluminescence measurements combined with annealing and/or ion milling were used to study the electrical and optical properties of HgCdTe films grown by molecular-beam epitaxy on GaAs substrates with ZnTe and CdTe buffer layers. Unintentional donor doping, likely from the substrate, which resulted in residual donor concentration of the order of 1015 cm−3, was observed in the films. Also, acceptor states, possibly related to structural defects, were observed.

Effect of N/Ga Flux Ratio in GaN Buffer Layer Growth by MBE on (0001) Sapphire on Defect Formation in the GaN Main Layer

1999 ◽  
Vol 572 ◽  
Author(s):  
S. Ruvimov ◽  
Z. Liliental-Weber ◽  
J. Washburn ◽  
Y. Kim ◽  
G. S. Sudhir ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Buffer Layer ◽  
Defect Formation ◽  
Flux Ratio ◽  
Growth Conditions ◽  
Buffer Layers ◽  
Simultaneous Increase ◽  
Growth Stages ◽  
Dislocation Generation ◽  
Gan Buffer Layer

ABSTRACTTransmission electron microscopy was employed to study the effect of N/Ga flux ratio in the growth of GaN buffer layers on the structure of GaN epitaxial layers grown by molecular-beamepitaxy (MBE) on sapphire. The dislocation density in GaN layers was found to increase from 1×1010 to 6×1010 cm−2 with increase of the nitrogen flux from 5 to 35 sccm during the growth of the GaN buffer layer with otherwise the same growth conditions. All GaN layers were found to contain inversion domain boundaries (IDBs) originated at the interface with sapphire and propagated up to the layer surface. Formation of IDBs was often associated with specific defects at the interface with the substrate. Dislocation generation and annihilation were shown to be mainly growth-related processes and, hence, can be controlled by the growth conditions, especially during the first growth stages. The decrease of electron Hall mobility and the simultaneous increase of the intensity of “green” luminescence with increasing dislocation density suggest that dislocation-related deep levels are created in the bandgap.

scholarly journals CURRENT COLLAPSE MEASUREMENTS IN PULSED GAN TRANSISTORS

2020 ◽  
Vol 259 (4) ◽  
pp. 12-18
Author(s):  
I. M. Abolduev ◽  
N. V. Alkeev ◽  
V. S. Belyaev ◽  
E. V. Kaevitser ◽  
I. D. Kashlakov
Keyword(s):  
Initial Data ◽  
Technological Process ◽  
Semiconductor Device ◽  
Thermal Characteristics ◽  
Gan Hemt ◽  
Current Collapse ◽  
Operation Modes ◽  
Current Voltage ◽  
And Behavior ◽  
Insight Into

The article discusses the issues of design and methodology related to the current-voltage (I-V) characteristics of a GaN HEMT. Reliable I-V characteristics show the operability of a semiconductor device, provide initial data for functional application of the device, and provide insight into the quality and reproducibility of the technological process. The type and behavior of I–V characteristics are influenced by the design and technological features of a GaN HEMT. Measurements of I-V characteristics in continuous and pulsed operation modes provide more details about the electrical and thermal characteristics of the devices under study.

Application of ZnO to Passivate the GaN-based Device Structures

2007 ◽  
Vol 1035 ◽  
Author(s):  
Eliana Kaminska ◽  
Anna Piotrowska ◽  
Marie-Antoinette di Forte Poisson ◽  
Sylvain Delage ◽  
Hacene Lahreche ◽  
...  
Keyword(s):  
Thin Films ◽  
Sputter Deposition ◽  
High Resistivity ◽  
Leakage Currents ◽  
Gan Hemt ◽  
Reactive Sputter Deposition ◽  
Device Structures ◽  
Hygroscopic Nature ◽  
Output Characteristics ◽  
Lattice Matched

AbstractThe fabrication of high-resistivity ZnO-based thin films lattice-matched to AlGaN/GaN structures has been developed. It relies on low-temperature reactive sputter deposition of ZnO:Sb from ZnSb target. Taking into account the hygroscopic nature of ZnO surface, an additional coating by Si3N4 films is applied to ensure the humidity protecition. The developped passivation suppresses leakage currents in Schottky diods, and substantially improves output characteristics of AlGaN/GaN HEMT.

Observations on the Morbid Anatomy of Mental Disease

1910 ◽  
Vol 56 (233) ◽  
pp. 227-253 ◽  
Author(s):  
George A. Watson
Keyword(s):  
Mental Disease ◽  
Close Correlation ◽  
Mental States ◽  
The Other ◽  
Cerebral Hemispheres ◽  
Structural Defects ◽  
Morbid Anatomy ◽  
The One ◽  
The Relationship

The following observations are founded upon the records of 301 autopsies performed by myself at Rainhill Asylum. They are concerned principally with certain abnormal and morbid manifestations which occur within the crania of the insane. Of these the chief are, on the one hand, indications of subevolution, as shown by macroscopic structural defects of the cerebral hemispheres, such as deficiency of weight or of convolutional complexity, and on the other, evidence of dissolution as exhibited by wasting of the cerebral hemispheres. The relationship existing between these abnormal and morbid manifestations and certain other intracranial appearances is also discussed. No attempt, however, has been made—for reasons which will afterwards be given—at any close correlation between these abnormal and morbid manifestations and the mental states recorded during life. The observations, therefore, are of a pathological rather than a clinical nature.

Inclined Substrate Deposition by Evaporation of Magnesium Oxide for Coated Conductors

1999 ◽  
Vol 585 ◽  
Author(s):  
Markus Bauer ◽  
Ralf Metzger ◽  
Robert Semerad ◽  
Paul Berberich ◽  
Helmut Kinder
Keyword(s):  
Electron Microscopy ◽  
Coated Conductors ◽  
The Other ◽  
Buffer Layers ◽  
Columnar Growth ◽  
Initial Momentum ◽  
3D Monte Carlo ◽  
Deposition Direction ◽  
Angle Deposition ◽  
Scanning Electron

AbstractBiaxially textured MgO buffer layers were deposited on metal substrates using “inclined substrate deposition” (ISD). The influence of the substrate inclination angle, deposition rate, and film thickness on the texture is shown. Scanning electron microscopy reveals columnar growth. We developed a growth model to explain the texturing. To test this model we have carried out 3D Monte-Carlo simulations. We find that the preferred orientation arises from mutual shadowing of the columns and directional surface diffusion due to their initial momentum.YBa2Cu3O7 (YBCO) films deposited on the ISD buffer layers are highly textured. The ab-planes of the YBCO are tilted with respect to the surface by typically 25° towards the direction of MgO vapor incidence. Therefore, the critical current density jc is anisotropic with up to 8 × 105 MA/cm2 in one direction and 4 × 105 MA/cm2 in the other. For tape coating the MgO deposition direction can be chosen so that the high jc is along the tape.

Structural Defects and Their Relationship to Nucleation of Gan Thin Films

1996 ◽  
Vol 423 ◽  
Author(s):  
Weida Gian ◽  
Marek Skowronski ◽  
Greg S. Rohrer
Keyword(s):  
Film Growth ◽  
Three Dimensional ◽  
Scanning Force Microscopy ◽  
Columnar Structure ◽  
Layer Growth ◽  
Buffer Layers ◽  
Structural Defects ◽  
Layer By Layer ◽  
Extended Defects ◽  
Edge Dislocations

AbstractMicrostructure and extended defects in α-GaN films grown by organometallic vapor phase epitaxy on sapphire substrates using low temperature AIN (or GaN) buffer layers have been studied using transmission electron microscopy. The types and distribution of extended defects were correlated with the film growth mode and the layer nucleation mechanism which was characterized by scanning force microscopy. The nature of the extended defects was directly related to the initial three-dimensional growth. It was found that inhomogeneous nucleation leads to a grain-like structure in the buffer; the GaN films then have a columnar structure with a high density of straight edge dislocations at grain boundaries which are less likely to be suppressed by common annihilation mechanisms. Layer-by-layer growth proceeds in many individual islands which is evidenced by the observation of hexagonal growth hillocks. Each growth hillock has an open-core screw dislocation at its center which emits monolayer-height spiral steps.

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