Deep Levels in Superlattices

1989 ◽  
Vol 163 ◽  
Author(s):  
John D. Dow ◽  
Shang Yuan Ren ◽  
Jun Shen ◽  
Min-Hsiung Tsai
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Deep Level ◽  
Energy Levels ◽  
Deep Trap ◽  
Shallow Donor ◽  
Deep Levels ◽  
Band Gap Engineering ◽  
Substitutional Impurities ◽  
Superlattice Period

AbstractThe physics of deep levels in semiconductors is reviewed, with emphasis on the fact that all substitutional impurities produce deep levels - some of which may not lie within the fundamental band gap. The character of a dopant changes when one of the deep levels moves into or out of the fundamental gap in response to a perturbation such as pressure or change of host composition. For example, Si on a Ga site in GaAs is a shallow donor, but becomes a deep trap for x>0.3 in AℓxGa1-xAs. Such shallow-deep transitions can be induced in superlattices by changing the period-widths and quantum confinement. A good rule of thumb for deep levels in superlattices is that the energy levels with respect to vacuum are relatively insensitive (on a >0.1 eV scale) to superlattice period-widths, but that the band edges of the superlattices are sensitive to changes of period. Hence the deep level positions relative to the band edges are sensitive to the period-widths, and shallow-deep transitions can be induced by band-gap engineering the superlattice periods.

Shallow and Deep Level Defects in GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
W. Götz ◽  
N.M. Johnson ◽  
D.P. Bour ◽  
C. Chen ◽  
H. Liu ◽  
...  
Keyword(s):  
Deep Level ◽  
Variable Temperature ◽  
Shallow Donor ◽  
Deep Levels ◽  
Electron Photoemission ◽  
Hall Effect Measurements ◽  
Transient Spectroscopy ◽  
P Type ◽  
Capacitance Transient ◽  
Threshold Energies

ABSTRACTShallow and deep electronic defects in MOCVD-grown GaN were characterized by variable temperature Hall effect measurements, deep level transient spectroscopy (DLTS) and photoemission capacitance transient spectroscopy (O-DLTS). Unintentionally and Si-doped, n-type and Mg-doped, p-type GaN films were studied. Si introduces a shallow donor level into the band gap of GaN at ∼Ec - 0.02 eV and was found to be the dominant donor impurity in our unintentionally doped material. Mg is the shallowest acceptor in GaN identified to date with an electronic level at ∼Ev + 0.2 eV. With DLTS deep levels were detected in n-type and p-type GaN and with O-DLTS we demonstrate several deep levels with optical threshold energies for electron photoemission in the range between 0.87 and 1.59 eV in n-type GaN.

scholarly journals Chemical trends of deep levels in van der Waals semiconductors

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Penghong Ci ◽  
Xuezeng Tian ◽  
Jun Kang ◽  
Anthony Salazar ◽  
Kazutaka Eriguchi ◽  
...  
Keyword(s):  
Deep Level ◽  
Energy Levels ◽  
Van Der Waals ◽  
Deep Levels ◽  
Persistent Photoconductivity ◽  
Sulfur Vacancy ◽  
Native Defects ◽  
Crystal Imperfections ◽  
Dx Center ◽  
Chemical Trends

AbstractProperties of semiconductors are largely defined by crystal imperfections including native defects. Van der Waals (vdW) semiconductors, a newly emerged class of materials, are no exception: defects exist even in the purest materials and strongly affect their electrical, optical, magnetic, catalytic and sensing properties. However, unlike conventional semiconductors where energy levels of defects are well documented, they are experimentally unknown in even the best studied vdW semiconductors, impeding the understanding and utilization of these materials. Here, we directly evaluate deep levels and their chemical trends in the bandgap of MoS2, WS2 and their alloys by transient spectroscopic study. One of the deep levels is found to follow the conduction band minimum of each host, attributed to the native sulfur vacancy. A switchable, DX center - like deep level has also been identified, whose energy lines up instead on a fixed level across different hosts, explaining a persistent photoconductivity above 400 K.

DEEP LEVELS DUE TO VACANCY PAIRS IN SILICON

1989 ◽  
Vol 03 (06) ◽  
pp. 863-870 ◽  
Author(s):  
HONGQI XU ◽  
U. LINDEFELT
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
State Energy ◽  
Energy Levels ◽  
Mean Value ◽  
Deep Levels ◽  
Nearest Neighbour ◽  
Recursion Method ◽  
The Mean ◽  
The Many

The recursion method is used to investigate the electronic structure of undistorted vacancy pairs in silicon up to the seventh nearest-neighbour divacancy. The many energy levels associated with these vacancy pairs in and around the band gap region are calculated. The results of the calculation show that the strength of the interaction between a pair of vacancies depends as much on their relative positions as on the inter-vacancy distance, but the mean value of the gap-state energy levels remains essentially constant at the monovacancy level.

Defects in Superlattices Under Pressure

1986 ◽  
Vol 77 ◽  
Author(s):  
Run-Di Hong ◽  
David W. Jenkins ◽  
S. Y. Ren ◽  
John D. Dow
Keyword(s):  
Hydrostatic Pressure ◽  
Quantum Well ◽  
Phase Boundary ◽  
Band Gap ◽  
Phase Diagrams ◽  
Conduction Band ◽  
Deep Level ◽  
Theoretical Calculations ◽  
Deep Trap ◽  
Quantum Well Width

ABSTRACTWe report theoretical calculations of deep levels in GaAs/AlxGa1−xAs superlattices under hydrostatic pressure. We predict phase diagrams for DX centers: for a given composition x there is a function p(a), which relates pressure p and GaAs quantum-well width a, and defines a phase boundary between two regions: one in which DX is a deep trap in the fundamental band gap and another in which the DX deep level lies in the conduction band.

Metal In-Diffusion during Fe and Co-Germanidation of Germanium

2007 ◽  
Vol 131-133 ◽  
pp. 47-52 ◽  
Author(s):  
Eddy Simoen ◽  
K. Opsomer ◽  
Cor Claeys ◽  
Karen Maex ◽  
Christophe Detavernier ◽  
...  
Keyword(s):  
Band Gap ◽  
Barrier Height ◽  
Rapid Thermal Annealing ◽  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Reverse Current ◽  
Deep Levels ◽  
Schottky Barriers ◽  
Deep Acceptor ◽  
Transient Spectroscopy

In this paper, the deep levels occurring in Fe- or Co-germanide Schottky barriers on ntype Ge have been studied by Deep Level Transient Spectroscopy (DLTS). As is shown, no traps have been found for germanidation temperatures up to 500 oC, suggesting that in both cases no marked metal in-diffusion takes place during the Rapid Thermal Annealing (RTA) step. Deep acceptor states in the upper half of the Ge band gap and belonging to substitutional Co and Fe can be detected by DLTS only at higher RTA temperatures (TRTA). For the highest TRTA, deep levels belonging to other metal contaminants (Cu) have been observed as well. Simultaneously, the reverse current of the Schottky barriers increases with TRTA, while the barrier height is also strongly affected.

Deep Levels in Type-II Superlattices

1993 ◽  
Vol 325 ◽  
Author(s):  
John D. Dow ◽  
Jun Shen ◽  
Shang Yuan Ren ◽  
William E. Packard
Keyword(s):  
Quantum Wells ◽  
High Speed ◽  
Deep Level ◽  
Deep Levels ◽  
Band Edge ◽  
Length Scale ◽  
Type Ii ◽  
Band Gap Engineering ◽  
Anion Site ◽  
And Control

AbstractQuantum confinement in superlattices affects shallow levels and band edges considerably (length scale of order 100 Å), but not deep levels (length scale of order 5 Å). Thus by band-gap engineering, one can move a band edge through a deep level, causing the defect responsible for the level to change its doping character. For example, the cation-on-anion-site defect in AlxGa1−xSb alloys is predicted to change from a shallow acceptor to a deep acceptor-like trap as the valence band edge passes through its T2 deep level with increasing At alloy content x. In a, Type-II superlattice, such as InAs/AlxGa1−xSb for x>0.2, where the conduction band minimum of the InAs should lie energetically below the antisite defect's T2 level in bulk AlxGa1−xSb, the electrons normally trapped in this deep level (when the defect is neutral) remotely dope the InAs n-type in the superlattice, leaving the defect positively charged. Thus a native defect that is thought of as an acceptor can actually be a donor and control the n-type doping of InAs quantum wells. The physics of such deep levels in superlattices and in quantum wells is summarized, and related to high-speed devices.

Profiling the Deep Trap Level in the Semiconductor Heterostructures by Small-Pulse Deep Level Transient Spectroscopy

1994 ◽  
Vol 338 ◽  
Author(s):  
Zhang Rong ◽  
Yang Kai ◽  
Qing Guoyi ◽  
Shi Yi ◽  
Gu Shulin ◽  
...  
Keyword(s):  
Deep Level ◽  
Deep Trap ◽  
Good Method ◽  
Deep Levels ◽  
Semiconductor Heterostructures ◽  
Trap Level ◽  
Narrow Gap ◽  
Transient Spectroscopy ◽  
First Time ◽  
Doping Condition

ABSTRACTIn this paper we report for the first time theoretical and experimental study on smallpulse DLTS measurements of deep levels in semiconductor heterostructures. A theoretical model has been developed on the basis of the Schodinger and Poisson's electrostatic equation. Distribution of charge density in the superlattice has been considered, especially transferred charges in the “narrow gap” sublayers. The calculated results indicate that tinder the 1017/cm3 doping condition, a 30mV small pulse corresponds to a 2nm “sampling space window”, it is enough to detect special signal of deep levels in each sublayer in the semiconductor heterostructures. A SiGe/Si sample has been measured by the small-pulse DLTS. The experimental results agree well with the theoretical prediction and show that the small-pulse DLTS is a good method to study deep levels in the semiconductor heterostructures.

Band gap engineering of graphene through quantum confinement and edge distortions

2016 ◽  
Vol 65 (2) ◽  
pp. 579-584 ◽  
Author(s):  
Luis Villamagua ◽  
Manuela Carini ◽  
Arvids Stashans ◽  
Cristian Vacacela Gomez
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Band Gap Engineering

Quantum confinement effects and band gap engineering of SnO2 nanocrystals in a MgO matrix

2012 ◽  
Vol 60 (3) ◽  
pp. 1072-1078 ◽  
Author(s):  
M.B. Sahana ◽  
C. Sudakar ◽  
A. Dixit ◽  
J.S. Thakur ◽  
R. Naik ◽  
...  
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Confinement Effects ◽  
Band Gap Engineering ◽  
Sno2 Nanocrystals ◽  
Quantum Confinement Effects
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