Properties of DX Centers in AlxGa1−xAs and Effects on Heterojunction Devices

1990 ◽  
Vol 184 ◽  
Author(s):  
P. M. Mooney
Keyword(s):  
Experimental Results ◽  
Dx Centers ◽  
Local Atomic Environment ◽  
Heterojunction Devices ◽  
Microscopic Models ◽  
Device Structures ◽  
Heterojunction Device ◽  
Dx Center

ABSTRACTIn this paper the effects of DX levels on the properties of AlxGa1−xAs and certain heterojunction device structures are summarized. Studies of alloy effects, variations of the local atomic environment near the donor, are reviewed and microscopic models of the DX center are discussed in terms of these and other recent experimental results.

Electrochemical C-V profiling of heterojunction device structures

1989 ◽  
Vol 36 (2) ◽  
pp. 309-313 ◽  
Author(s):  
A.C. Seabaugh ◽  
W.R. Frensley ◽  
R.J. Matyi ◽  
G.E. Cabaniss
Keyword(s):  
Device Structures ◽  
Heterojunction Device

Electrical characteristics of lateral organic bulk heterojunction device structures

2012 ◽  
Vol 13 (7) ◽  
pp. 1185-1191 ◽  
Author(s):  
Christopher Lombardo ◽  
Zi-En Ooi ◽  
Eric Danielson ◽  
Ananth Dodabalapur
Keyword(s):  
Bulk Heterojunction ◽  
Electrical Characteristics ◽  
Device Structures ◽  
Heterojunction Device

scholarly journals A Photocapture Test of DX-Center Models

1989 ◽  
Vol 163 ◽  
Author(s):  
Harold P. Hjalmarson ◽  
S. R. Kurtz ◽  
T. M. Brennan
Keyword(s):  
Conduction Band ◽  
Cross Section ◽  
Threshold Energy ◽  
Photoionization Cross Section ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Null Result ◽  
Dx Center

AbstractThe DX-center model is widely used to explain data for the persistent photoconductivity (PPC) effect. An analysis of the DX-center model suggests a new experiment to test its correctness. In this experiment, photons near the threshold energy of the photoionization cross-section for the DX-center induce transitions from the partially occupied conduction band to empty DX-centers. This mechanism, which we call photocapture, competes with the usual photoionization which empties the DX-centers. The photocapture cross-section is estimated and an experimental attempt is made to detect photocapture. The significance of the null result is discussed.

Evidence for Metastabile State of DX Center in AxGa1-xAs

1992 ◽  
Vol 262 ◽  
Author(s):  
Subhasis Ghosh ◽  
Vikram Kumar
Keyword(s):  
Activation Energy ◽  
Deep Level Transient Spectroscopy ◽  
Thermal Activation ◽  
Deep Level ◽  
Thermal Activation Energy ◽  
Dx Centers ◽  
Dx Center ◽  
Transient Spectroscopy ◽  
Silicon Doped ◽  
First Time

ABSTRACTPhoto-Deep Level Transient Spectroscopy with 1.38 eV light reveals a new level with thermal activation energy 0.2 eV of DX centers in silicon doped Alx Ga1-xAs (x = 0.26) for the first time. The observation of this level directly proves the negative-U properties of DX centers and the existence of thermodynamically metastable state DX.

SIGNIFICANCE OF DX-CENTERS FOR ACOUSTIC INDUCED RECONSTRUCTION PROCESSES OF DEFECTS IN GaN/AlGaN

2021 ◽  
Vol 56 ◽  
pp. 61-70
Author(s):  
Ya. M. Olikh ◽  
Keyword(s):  
Electron Concentration ◽  
Lattice Parameter ◽  
Central Position ◽  
Loading Frequency ◽  
Acoustic Action ◽  
Effective Electron ◽  
Dx Centers ◽  
Centrally Symmetric ◽  
Dx Center ◽  
Action Process

The experimental results of amplitude effects are compared (from an ultrasonic wave deformation amplitude – a tension τUS) for electron concentration and changes of the lattice parameter on the same sample GaN/Al0.2Ga0.8N/GaN/AlN. It has been experimentally established that at ultrasonic loading (frequency 5–10 MHz, amplitude – towards 2·104 W/m2) there is a nonlinear increase in the effective electron concentration and an increase in the lattice parameter; at the same time, the mobility of electrons decreases and μН(τUS) ~ |τUS|. The energy parameters of the acoustic activation charge carriers process are calculated from the approximation of experimental amplitude changes – Еа ≈ 50 meV and γn(300 K) ≈ 2,5·10-27 m3. The amplitude dependences (increase) of the relative lattice parameter change (ΔС/С) from the tension τUS have been investigated experimentally at different frequencies. The energy of DX-center transition UDX ≈ 108 meV and the activation volume of this transition γDX ≈ 6,6·10-27 m3 are calculated from the approximation of the experimental amplitude changes. The revealed correlation of the magnitude of acoustic induced effects in different experiments allows to build a quantitative energy model of the acoustic action process based on the properties of metastable DX centers. It is shown that the acoustic induced process occurs due to the dimensional displacement of the DX-center atom (a background impurity of silicon atoms) from the non-central position to the centrally symmetric one; herewith DX-center is ionized, one goes into the d0-state. It is believed that the changes are most likely to occur near penetrating dislocations in the barrier layer Al0.2Ga0.8N – acoustic modulated oscillations of the distance between the possible positions of the donor atom lead to a decrease in the barrier to the displacement of the defect.

COMPARISON OF TWO-NEUTRON TRANSFER INTENSITIES IN RARE EARTH NUCLEI WITH PREDICTIONS OF MICROSCOPIC MODELS

1995 ◽  
Vol 04 (02) ◽  
pp. 411-418 ◽  
Author(s):  
A.A. SHIHAB-ELDIN ◽  
J.O. RASMUSSEN ◽  
M.A. STOYER ◽  
D.G. BURKE ◽  
P.E. GARRETT
Keyword(s):  
Rare Earth ◽  
Single Particle ◽  
Exact Diagonalization ◽  
Experimental Results ◽  
Microscopic Structure ◽  
Neutron Transfer ◽  
Microscopic Description ◽  
Model Calculations ◽  
Microscopic Models ◽  
Rare Earth Nuclei

The microscopic structure of 0+ states in well-deformed even-even nuclei was generated within a framework of exact diagonalization of the residual pairing and n−p forces in a seniority-zero Nilsson orbital basis. Available experimental results on the fraction of the L=0 two-neutron transfer intensity which goes to excited 0+ states are compared with microscopic model calculations, giving good overall agreement. Some prominent features of the experimental systematics appear to depend on details of the single-particle states, and are therefore better explained with a microscopic description than with the IBM.

scholarly journals Large Persistent Photochromic Effect Due to DX Centers in AlSb Doped with Selenium

1995 ◽  
Vol 378 ◽  
Author(s):  
P. Becla ◽  
A. G. Witt ◽  
J. Lagowski ◽  
W. Walukiewicz
Keyword(s):  
Absorption Coefficient ◽  
Conduction Band ◽  
Spectral Range ◽  
Donor Level ◽  
Dx Centers ◽  
Enhanced Absorption ◽  
Photochromic Effect ◽  
Dx Center

AbstractA large photochromic effect has been observed in bulk AlSb crystals doped with Se. Illumination with the light of energy higher than 1 eV leads to an increase of the absorption coefficient in the spectral range 0.1 eV to 1.6 eV. The enhanced absorption is persistent at the temperatures below about 100 K. The effect is a manifestation of a DX-like bistability of Se donors. The illumination transfers the electrons from the DX center to a metastable hydrogenic level. The increased absorption with peaks around 0.2 eV and 0.5 eV is due to photoionization from the donor level to X1 and X3 minima of the conduction band

Comprehensive Kinetic of Defects in a-SI:H

1991 ◽  
Vol 219 ◽  
Author(s):  
David Redfield ◽  
Richard H. Bube
Keyword(s):  
Solar Cells ◽  
Steady State ◽  
Light Intensity ◽  
Rate Equation ◽  
Defect Density ◽  
Microscopic Models ◽  
Dx Center ◽  
Stretched Exponentials ◽  
Kinetics Of ◽  
Insight Into

ABSTRACTLThe introduction of several new principles into the analysis of transition kinetics of metastable defects in a-Si:H has produced substantially improved rate equation for the density of defects as functions of time, light intensity, and temperature. The solution of this equation is stretched exponential (SE) having properties that explain in unifying way many observations of defect properties, including generation and anneal of the defect density in homogeneous films and degradation and anneal of solar cells. Major consequences are found for both the steady-state and transient properties of the defect density and for interpretations of microscopic models of the defects. These properties are also shown to be analogous to those of metastable centers in other materials, particularly the metastable DX center in AlGaAs which offers rare insight into the microscopic origins of stretched exponentials that can be applied to a-Si:H in ways that provide new perspectives on effects of alloying and hydrogen on stability.

DX Center Energy Level in InxAl1−xAs Compounds

1999 ◽  
Vol 573 ◽  
Author(s):  
Hüseyin Sari ◽  
Harry H. wieder
Keyword(s):  
Energy Level ◽  
Conduction Band ◽  
Canonical Ensemble ◽  
Grand Canonical Ensemble ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Indium Concentration ◽  
Self Consistent ◽  
Dx Center ◽  
Grand Canonical

ABSTRACTThe presence of DX centers in InxAl1−xAs, primarily in the indirect portion of the InxAl1−xAs bandgap, has been determined using modulation doped InxAl1−xAs/InyGa1−yAs heterostructures by means of persistent photoconductivity (PPC) and galvanomagnetic measurements. From the cooling bias experiment, the PPC, and self consistent Poisson and Schrddinger simulations the ratio of the ionized shallow donors to the DX centers is obtained. Using this ratio in the grand canonical ensemble (GCE) the energy level of DX centers is determined. It is found that the DX energy level merges with the conduction band at x ≅ 0.42 and is resonant with the conduction band in higher indium concentration.

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