New Defect Related Phenomena in Semiconductor Heterolayers and Superlattices

1987 ◽  
Vol 104 ◽  
Author(s):  
Federico Capasso ◽  
Fabio Beltram
Keyword(s):  
Band Structure ◽  
Quantum Well ◽  
Quantum Wells ◽  
Recent Work ◽  
Quantum Well Structures ◽  
Deep Centers ◽  
Deep Traps ◽  
Structure Engineering

ABSTRACTRecent work on defect related phenomena in heterojunctions and quantum well structures is reviewed. These include situations in which quantum wells behave as deep traps and the use of shallow and deep centers as new tools for band structure engineering. Among the latter tunable band discontinuities and the artificial tailoring of superlattice states via δ-doping techniques are discussed.

Photoluminescence Fatigue in Laterally-Ordered (GaP)2/(InP)2 Short-Period-Superlattices (SPS) Grown by Molecular Beam Epitaxy

1993 ◽  
Vol 325 ◽  
Author(s):  
X. C. Liu ◽  
S. Q. Gu ◽  
E. E. Reuter ◽  
S. G. Bishop ◽  
A. C. Chen ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Quantum Well ◽  
Quantum Wells ◽  
Lower Energy ◽  
Molecular Beam ◽  
Continuous Illumination ◽  
Exciting Light ◽  
Quantum Well Structures ◽  
Short Period ◽  
Short Period Superlattices

AbstractSpontaneously laterally ordered (GaP)2/(InP)2 short period superlattices (SPS) grown by Molecular Beam Epitaxy (MBE) on nominal (100) GaAs substrates have been studied by photoluminescence (PL) spectroscopy. The samples studied included SPS comprising 110 pairs of (GaP)2/(InP)2 (total thickness σ90 nm) and multiquantum well structures in which quantum wells comprising 12 pairs of (GaP)2/(InP)2 SPS layers (thickness σ10 nm) are alternated with lattice-matched GaInP random alloy barrier layers. The 5K PL spectra include a σ1760 meV nearband edge band, and a much broader, lower energy (σ1670 meV) luminescence band that exhibits an unusual fatiguing behavior; its intensity diminishes monotonically during continuous illumination by the exciting light. This fatigued PL state is metastable at low temperatures. In the quantum well structure, although the relative intensity of the lower energy band is significantly weaker in comparison to the higher one, the fatiguing behavior still exists. However the fatiguing rate is slower in quantum well structures than that observed in the thick SPS film.

A THEORETICAL AND EXPERIMENTAL STUDY OF ELECTRONIC CONFINEMENT, COUPLING, AND TRANSLAYER INTERACTION IN NOBLE-METAL QUANTUM-WELL STRUCTURES

1994 ◽  
Vol 08 (18) ◽  
pp. 1075-1096 ◽  
Author(s):  
W. E. MCMAHON ◽  
T. MILLER ◽  
T.-C. CHIANG
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Noble Metal ◽  
Experimental Studies ◽  
Surface States ◽  
Double Quantum ◽  
Multilayer Systems ◽  
Quantum Well Structures ◽  
Double Quantum Well ◽  
Bloch Electrons

Noble-metal multilayer systems have been grown and examined with angle-resolved photoemission. Surface states, and single and double quantum wells have been studied experimentally; the results can be explained with a simple theoretical model based upon Bloch electrons. In this paper, we will present our model and then give a description of some experimental studies which utilize the model. In particular, we will consider double-quantum-well systems which can be used to examine basic aspects of electronic confinement, layer–layer coupling, and translayer interaction through a barrier.

scholarly journals Thermal Annealing of InGaN/GaN Strained-Layer Quantum Well

1999 ◽  
Vol 4 (S1) ◽  
pp. 642-647
Author(s):  
Michael C.Y. Chan ◽  
Kwok-On Tsang ◽  
E. Herbert Li ◽  
Steven P. Denbaars
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Quantum Well ◽  
Thermal Annealing ◽  
Diffusion Coefficients ◽  
Green Light ◽  
Optical Gain ◽  
Quantum Well Structures ◽  
Strained Layer ◽  
Constant Diffusion

Quantum well (QW) material engineering has attracted a considerable amount of interest from many people because of its ability to produce a number of optoelectronic devices. QW composition intermixing is a thermal induced interdiffusion of the constituent atoms through the hetero-interface. The intermixing process is an attractive way to achieve the modification of the QW band structure. It is known that the band structure is a fundamental determinant for such electronic and optical properties of materials as the optical gain, the refractive index and the absorption. During the process, the as-grown square-QW compositional profile is modified to a graded profile, thereby altering the confinement profile and the subband structure in the QW. The blue-shifting of the wavelength in the intermixed QW structure is found in this process.In recent years, III-nitride semiconductors have attracted much attention. This is mainly due to their large bandgap range from 1.89eV (wurtzite InN) to 3.44eV (wurtzite GaN). InGaN/GaN quantum well structures have been used to achieve high lumens blue and green light emitting diodes. Such structures also facilitate the production of full colour LED displays by complementing the colour spectrum of available LEDs.In this paper, the effects of thermal annealing on the strained-layer InGaN/GaN QW will be presented. The effects of intermixing on the confinement potential of InGaN/GaN QWs have been theoretically analysed, with sublattices interdiffusion as the basis. This process is described by Fick’s law, with constant diffusion coefficients in both the well and the barrier layers. The diffusion coefficients depend on the annealing temperature, time and the activation energy of constituent atoms. The optical properties of intermixed InGaN/GaN QW structure of different interdiffusion rates have been theoretically analyzed for applications of novel optical devices. The photoluminescence studies and the intermixed QW modeling have been used to understand the effects of intermixing.

Optical Gain Spectra in InGaN/GaN Quantum Wells with the Compositional Fluctuations

1998 ◽  
Vol 537 ◽  
Author(s):  
Takeshi Uenoyama
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Optical Gain ◽  
Inhomogeneous Broadening ◽  
Localized States ◽  
Quantum Well Structures ◽  
Potential Fluctuation ◽  
Quantum Disk ◽  
Gain Spectra

The compositional fluctuations of the In content were found in InGaN/GaN quantum wells and it caused the localized states by the potential fluctuation. We have evaluated the optical gain of GaN based quantum well structures with localized states. The localized states are treated as the subband states of the quantum disk-like dots in the well. It was found that the inhomogeneous broadening played an important role in the optical gain and that it should be reduced to use the benefit of the localized states for laser oscillations.

AES and EELFS Studies of Initial Stages of Growth of GaAs/InAs/GaAs Heterostructures.

1988 ◽  
Vol 144 ◽  
Author(s):  
F. D. Schowengerdt ◽  
F. J. Grunthaner ◽  
John K. Liu
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Growth Parameters ◽  
High Energy ◽  
Model Calculations ◽  
Mbe Growth ◽  
Quantum Well Structures ◽  
Stages Of Growth ◽  
Double Heterostructures ◽  
Composition And Structure

ABSTRACTWe report on a systematic study of the composition and structure of GaAs/InAs/GaAs quantum wells using Auger Electron Spectroscopy (AES), Extended Energy Loss Fine Structure (EELFS), and Reflection High Energy Electron Diffraction (RHEED) techniques. Double heterostructures with InAs thickness ranging from 2 to 10 monolayers, capped by 2 to 10 monolayers of GaAs, were grown by MBE using a variety of techniques, including those employing sequential, interrupted, and delayed shutter timing sequences. AES peak ratios are compared with model calculations to monitor compositional development of the multilayers. The AES results are correlated with RHEED measurements to determine MBE growth parameters for optimal control of the stoichiometry and surface morphology. EELFS was used to monitor strain in the buried InAs layers. The AES results show departure from smooth laminar growth of layers of stoichiometric InAs on GaAs at temperatures below 420 C and above 470 C. AES results on the quantum well structures suggest floating InAs layers on top of the GaAs and/or facet formation in the GaAs layers. The EELFS results, when compared to bulk InAs, indicate the presence of strain in the buried InAs quantum well.

Optical evaluation of pretreated InGaN quantum well structures

2003 ◽  
Vol 798 ◽  
Author(s):  
T. Böttcher ◽  
F. Bertram ◽  
P. Bergman ◽  
A. Ueta ◽  
J. Christen ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Room Temperature ◽  
Growth Direction ◽  
Wetting Layer ◽  
Quantum Well Structures ◽  
Room Temperature Photoluminescence ◽  
Decay Times ◽  
Wavelength Distribution ◽  
Ingan Quantum Wells

ABSTRACTIn order to optimize the quantum efficiency of InGaN quantum wells, different MOVPE growth sequences are compared using photo- and electroluminescence. In one study, the surface was pretreated with trimethylindium (TMIn) prior to the well deposition. In another study, growth interruptions were performed after the quantum well deposition to desorb segregated indium. In both cases, the room-temperature photoluminescence (PL) intensity is strongly enhanced. For the samples grown with TMIn preflow the wavelength distribution in low-temperature cathodoluminescence (CL) wavelength mappings is narrowed, which can be attributed to more homogeneous quantum wells. Furthermore, the decay times of the radiative recombination increase both at RT and 2K. A reason for this could be an improved indium profile along the growth direction or a more homogeneous In wetting layer due to the pre-wetted surface.

scholarly journals Room temperature PL efficiency of InGaN/GaN quantum well structures with prelayers as a function of number of quantum wells

2016 ◽  
Vol 13 (5-6) ◽  
pp. 248-251 ◽  
Author(s):  
George M. Christian ◽  
Simon Hammersley ◽  
Matthew J. Davies ◽  
Philip Dawson ◽  
Menno J. Kappers ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Room Temperature ◽  
Quantum Well Structures

Buried Quantum Well Structure Fabricated by in Situ EB Lithography

1991 ◽  
Vol 236 ◽  
Author(s):  
H. Kawanishi ◽  
Y. Sugimoto ◽  
T. Ishikawa ◽  
N. Tanaka ◽  
H. Hidaka
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Gaas Surface ◽  
Photoluminescence Intensity ◽  
Positive Type ◽  
Quantum Well Structures ◽  
Lithography Process ◽  
Order Of Magnitude ◽  
Processed Sample

AbstractBuried quantum well structures have been fabricated in GaAs/AIGaAs system using an in situ lithography process. The process utilizes an ultrathin oxide layer formed in situ on a GaAs surface as a mask against Cl2 gas etching. An electron beam (EB)-induced Cl2 gas etching is used to locally remove the oxide mask for positive-type lithography. For negativetype lithography, the oxide mask is selectively formed on a GaAs surface by EB-stimulated oxidation. Subsequent Cl2 gas etching results in the formation of isolated quantum wells. After removing the oxide mask, overgrowth using molecular beam epitaxy is successfully carried out on the patterned surface. The cathodoluminescence image of the buried quantum well demonstrates the high quality of the resulting structure formed by this “in situ EB lithography” process. The photoluminescence intensity from the quantum well of the processed sample is proved to be the same order of magnitude compared with that from a successively grown sample, showing that the use of the oxide mask causes no serious degradation in the processed interface.

Conduction edge strain splitting in Ge-Si quantum wells using EELS

1993 ◽  
Vol 51 ◽  
pp. 816-817
Author(s):  
P.E. Batson ◽  
J.F. Morar
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Conduction Band ◽  
Lattice Mismatch ◽  
Axial Strain ◽  
Band Edge ◽  
Reference Level ◽  
Conduction Band Edge ◽  
Type I ◽  
Quantum Well Structures

Ge/Si quantum well structures show a high hole mobility as the heavy hole bands are shifted to lower energy under bi-axial strain produced by lattice mismatch between the well and the Si substrate. This strain can also split and shift the conduction band edge in the well to below that of Si, producing a Type I quantum well capable of photo-luminescence. In previous work, we have shown that the conduction bandstructure can be obtained using EELS in the relaxed Ge/Si alloy system. Also, we have noticed that the heterojunction band offset can be obtained from EELS because the Si 2p core level is a constant energy reference level throughout the alloy composition. In this report, we show that a detailed fitting of the shape of the Si L2,3 edge can obtain the bi-axial strain splitting of the conduction band edge as a function of position inside a quantum well. This information can then be correlated with annular dark field images of the cross sectioned well.

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