New Method of Computing Band Offsets and Its Application to AlGaN/GaN Heterostructures

1997 ◽  
Vol 482 ◽  
Author(s):  
Richard T. Webster ◽  
A. F. M. Anwar
Keyword(s):  
Experimental Data ◽  
Carrier Concentration ◽  
Valence Band ◽  
Mole Fraction ◽  
Close Agreement ◽  
Simple Technique ◽  
Piezoelectric Effect ◽  
Interface Charge ◽  
Band Alignments ◽  
Valence Band Discontinuity

AbstractCalculated sheet carrier concentration as a function of Al mole fraction in the quantum well (QW) formed at the GaN/AlGaN heterointerface is calculated and compared to experimental data. Close agreement between experiment and theory is observed. The calculated sheet carrier concentration reflects the maximum carrier concentration possible in the GaN QW for a given Al mole fraction and can not be used to argue in favor of either interface charge or piezoelectric effect as giving rise to the carriers. Based on experimental data the charge density in the AlGaN layer is estimated to be 4 × 1012cm-2The calculations are based upon a simple technique to determine valence band alignments. Calculated values are compared to experimental data showing excellent agreement. A calculated valence band discontinuity of 0.42eV for AlN/GaN is well within the experimental bounds.

NOVEL MEASUREMENT OF THE BAND DISCONTINUITIES IN (Al,Ga)As HETEROJUNCTIONS

1985 ◽  
Vol 56 ◽  
Author(s):  
B. A. WILSON ◽  
P. DAWSON ◽  
C. W. TU ◽  
R. C. MILLER
Keyword(s):  
Valence Band ◽  
Binding Energies ◽  
Band Alignment ◽  
Material System ◽  
Valence Band Offset ◽  
Quantum Well Structures ◽  
Accurate Knowledge ◽  
Novel Method ◽  
Band Alignments ◽  
Valence Band Discontinuity

AbstractA novel method has been used to obtain a direct and accurate measure of the valence-band discontinuity AlyGa1−yAs/AlAs heterojunctions in quantum-well structures. The technique takes advantage of the crossover occurring at a critical Al concentration above which the indirect X minimum in the AlAs becomes the lowest-energy conduction band in the system. Within these “staggered” band alignment structures, photoexcited electrons and holes are spatially separated, and recombination occurs across the interface. The resulting emission fixes the valence-band offset to within 1% without accurate knowledge of other system parameters, such as effective masses and exciton or dopant binding energies. These measurements represent the first direct optical confirmation of staggered band alignments in this technologically important material system.

p-InGaN/n-GaN Heterojunction Diodes and their Application to Heterojunction Bipolar Transistors

2000 ◽  
Vol 639 ◽  
Author(s):  
Toshiki Makimoto ◽  
Kazuhide Kumakura ◽  
Toshio Nishida ◽  
Naoki Kobayashi
Keyword(s):  
Valence Band ◽  
Breakdown Voltage ◽  
Mole Fraction ◽  
Heterojunction Bipolar Transistors ◽  
Room Temperature ◽  
Tunneling Current ◽  
Current Gain ◽  
Heterojunction Diodes ◽  
Hole Confinement ◽  
Valence Band Discontinuity

ABSTRACTp-InGaN/n-GaN heterojunction diodes were grown by metalorganic vapor phase epitaxy and characterized using current-voltage (I-V) and capacitance-voltage (C-V) measurements. We changed the In mole fraction in p-InGaN from 0 to 25% to investigate diode characteristics. All the diodes showed rectified I-V characteristics at room temperature. The ideality factors obtained from forward I-V characteristics were around 2, meaning that the recombination current is dominant instead of the tunneling current through the defects in depletion layers of the diodes. The breakdown voltage in reverse I-V characteristics depends on the net donor concentration (ND - NA) in n-GaN instead of the In mole fraction in p-InGaN. This result also means that the defects in p-InGaN do not influence the breakdown voltage. The built-in potential from C-V measurements decreases with the In mole fraction in p-InGaN, meaning that the valence band discontinuity increases with the In mole fraction. This valence band discontinuity realizes the hole confinement in an HBT with an p-InGaN base. Using these InGaN/GaN heterojunction diodes, an InGaN/GaN double heterojunction bipolar transistor was fabricated for the first time. The maximum current gain of 1.2 was obtained at room temperature.

scholarly journals Investigation of Band Alignment for Hybrid 2D-MoS2/3D-β-Ga2O3 Heterojunctions with Nitridation

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Ya-Wei Huan ◽  
Ke Xu ◽  
Wen-Jun Liu ◽  
Hao Zhang ◽  
Dmitriy Anatolyevich Golosov ◽  
...  
Keyword(s):  
Valence Band ◽  
Transition Metal Dichalcogenides ◽  
Three Dimensional ◽  
Optoelectronic Devices ◽  
Band Alignment ◽  
Band Offsets ◽  
Group Iii ◽  
Nanoelectronic Devices ◽  
Metal Dichalcogenides ◽  
Band Alignments

AbstractHybrid heterojunctions based on two-dimensional (2D) and conventional three-dimensional (3D) materials provide a promising way toward nanoelectronic devices with engineered features. In this work, we investigated the band alignment of a mixed-dimensional heterojunction composed of transferred MoS2 on β-Ga2O3($$ 2- $$2-01) with and without nitridation. The conduction and valence band offsets for unnitrided 2D-MoS2/3D-β-Ga2O3 heterojunction were determined to be respectively 0.43 ± 0.1 and 2.87 ± 0.1 eV. For the nitrided heterojunction, the conduction and valence band offsets were deduced to 0.68 ± 0.1 and 2.62 ± 0.1 eV, respectively. The modified band alignment could result from the dipole formed by charge transfer across the heterojunction interface. The effect of nitridation on the band alignments between group III oxides and transition metal dichalcogenides will supply feasible technical routes for designing their heterojunction-based electronic and optoelectronic devices.

Interface properties and valence-band discontinuity of MnS/ZnSe heterostructures

1996 ◽  
Vol 54 (4) ◽  
pp. 2718-2722 ◽  
Author(s):  
L. Wang ◽  
S. Sivananthan ◽  
R. Sporken ◽  
R. Caudano
Keyword(s):  
Valence Band ◽  
Interface Properties ◽  
Valence Band Discontinuity

TEMPERATURE DEPENDENCE OF THERMODYNAMIC PROPERTIES OF IONIC SOLIDS

2009 ◽  
Vol 23 (11) ◽  
pp. 2503-2509 ◽  
Author(s):  
S. K. SHARMA
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Volume Expansion ◽  
Close Agreement ◽  
Present Model ◽  
Expansion Ratio ◽  
Thermal Expansivity ◽  
Temperature Derivative ◽  
Computing Model ◽  
Ionic Solids

The present paper proposes a computing model for temperature dependence of volume thermal expansivity, volume expansion ratio and second order temperature derivative of volume based on the assumption that the product αKT remains constant at high temperatures and zero pressure. We have taken NaCl and KCl to testify the validity of the present model. A fairly close agreement between the calculated results and experimental data strongly supports the present model.

Growth and Characterization of the Binary Defect Alloy Cu2-xSe and the Relation to II–VI/I–III–VI Heterojunction Formation

1995 ◽  
Vol 378 ◽  
Author(s):  
Art J. Nelson ◽  
K. Sinha ◽  
John Moreland
Keyword(s):  
Electronic Structure ◽  
Valence Band ◽  
Photoemission Spectroscopy ◽  
Interfacial Chemistry ◽  
Valence Band Offset ◽  
Force Microscopy ◽  
Atomic Force ◽  
Valence Band Discontinuity

AbstractSynchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the CdS/Cu2Se heterojunction interface. Cu2−xSe layers were deposited on GaAs (100) by molecular beam epitaxy from Cu2Se sources. Raman spectra reveal a strong peak at 270 cm−1, indicative of the Cu2−xSe phase. Atomic force microscopy reveals uniaxial growth in a preferred (100) orientation. CdS overlayers were then deposited in-situ, at room temperature, in steps on these epilayers. Photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the Se3d and Cd4d core lines. The results were used to correlate the interfacial chemistry with the electronic structure and to directly determine the CdS/Cu2−xSe and heterojunction valence band discontinuity and the consequent heterojunction band diagram. These results are compared to the valence band offset (ΔEv) for the CdS/CuInSe2 heterojunction interface.

Volumetric Changes in Cells During Freezing and Thawing

1980 ◽  
Vol 102 (2) ◽  
pp. 91-97 ◽  
Author(s):  
J. M. Knox ◽  
G. S. Schwartz ◽  
K. R. Diller
Keyword(s):  
Experimental Data ◽  
Image Analysis ◽  
Close Agreement ◽  
Living Cells ◽  
Freezing Process ◽  
Freezing And Thawing ◽  
Image Analysis Technique ◽  
Computerized Image Analysis ◽  
Analysis Technique ◽  
Thawing Process

A thermodynamic model is presented to describe the combined freezing and thawing process for living cells. Continuous changes in the cell volume are predicted according to the thermal protocol imposed on the system. Experimental verification of the model is sought by monitoring continuously the volume of cells as frozen on a cryomicroscope. The volumes of individual cells are measured from sequential photomicrographs by a computerized image analysis technique. The model and experimental data are in quite close agreement for the freezing process, but upon thawing the experimentally measured volumes consistently increased much more rapidly than predicted by the model. The model can be made to conform to the data by accounting for a substantial influx of electrolyte to the cell at subfreezing temperatures.

Energy Loss for Swift Heavy Ions in Different Elemental Absorbers: A Different Approach for Effective Charge Parameterization

2015 ◽  
Vol 238 ◽  
pp. 196-205
Author(s):  
B. Rani ◽  
Kalpana Sharma ◽  
Neetu ◽  
Anupam ◽  
Shyam Kumar ◽  
...  
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Effective Charge ◽  
Heavy Ions ◽  
Close Agreement ◽  
Input Parameter ◽  
Quantum Mechanical ◽  
Swift Heavy Ions ◽  
Calculated Energy ◽  
Semi Empirical

The energy loss for swift heavy ions, covering Z=3-29(~0.2 - 5.0MeV/n), has been calculated in the elemental absorbers like C, Al and Ti. The present calculations are based on Bohr’s approach applicable in both classical and quantum mechanical regimes. The major input parameter, the effective charge, has been calculated in a different way without any empirical/semi-empirical parameterization. The calculated energy loss values have been compared with the available experimental data which results in a close agreement.

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