Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.

1990 ◽  
Vol 198 ◽  
Author(s):  
D.C. Houghton ◽  
N.L. Rowell
Keyword(s):  
Quantum Wells ◽  
Misfit Dislocation ◽  
Thermal Processing ◽  
Internal Quantum Efficiency ◽  
Dislocation Nucleation ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Dislocation Generation ◽  
Strained Layers ◽  
Wide Range

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.

Photoluminescence from Coherently Strained Si1−xGex Alloys

1990 ◽  
Vol 198 ◽  
Author(s):  
N.L. Rowell ◽  
J.-P. Noël ◽  
D.C. Houghton ◽  
D.D. Perovic
Keyword(s):  
Quantum Wells ◽  
Internal Quantum Efficiency ◽  
High Energy ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Strained Si ◽  
Strained Layers ◽  
Defect Complexes ◽  
Random Alloy

ABSTRACTAn intense, broad photoluminescence PL peak, with an internal quantum efficiency as high as 31%, has been observed from a variety of structures containing Si1−xGex strained layers on Si(100) substrates; i.e. Si1−xGex thick random alloy layers, single quantum wells (SQW) and multiple quantum wells (MQW) with layers thick enough so that zone folding effects were not relevant. This peak, which shifted consistently and predictably with Ge concentration( 0.06 < × < 0.53), had its high energy edge near the established band gap for strained SiGe. PL excitation spectroscopy indicated that no phonons were involved in the process causing the SiGe PL peak. Samples deposited at ~ 400 °C exhibited low PL intensity, whereas annealing at ~ 600 °C enhanced the intensity by as much as two orders of magnitude. This anneal treatment was found to remove grown-in defect complexes without creating a significant density of misfit dislocations. The PL peak energy at 4.2 K varied from 620 to 990 meV for Ge fractions x from 0.53 to 0.06. When the samples were forced to relax, e.g. by higher temperature annealing, the luminescence of this peak either shifted to near the relaxed bandgap or was quenched by deep, dislocation related states. Prior to such relaxation, the efficient PL was due to exciton accumulation in the strained Si1−xGex layers of single and multiple quantum wells, where the bandgap was locally reduced. It is suggested that the recombination of electrons and holes occuring within a high-density electron hole condensate (EHC) can cause the observed spectrum.

“Barrierless” Misfit Dislocation Nucleation in SiGe/Si Strained Layer Epitaxy

1992 ◽  
Vol 263 ◽  
Author(s):  
D.D. Perovic ◽  
D.C. Houghton
Keyword(s):  
Activation Energy ◽  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Theoretical Treatment ◽  
Misfit Dislocations ◽  
Plan View ◽  
Strained Layer ◽  
Wide Range ◽  
Peierls Barrier

ABSTRACTThe study of the critical thickness/strain phenomenon inherent in metastable, layered heterostructures has led to the development of several models which describe elastic strain relaxation. Hitherto, the nucleation of misfit dislocations required for coherency breakdown is the least well understood aspect of strain relaxation, due to the paucity of experimental data. Moreover, existing theoretical calculations predict relatively large activation energy barriers (>10 eV) for misfit dislocation nucleation in relatively low misfit (<2%) systems. In this work it will be shown that the nucleation of misfit dislocations can occur spontaneously demonstrating a vanishingly small activation energy barrier. Specifically, experimental studies of a wide range of GexSi1−x/Si (x< 0.5) hetero-structures, grown by MBE and CVD techniques, have provided quantitative data from bulk specimens on the observed misfit dislocation nucleation rate and activation energy using large-area diagnostic techniques (eg. chemical etching/Nomarski microscopy). In parallel, the strained layer microstructure was studied in detail using crosssectional and plan-view electron microscopy in order to identify a new dislocation nucleation mechanism, the ‘double half-loop’ source. From the combined macroscopic and microscopic analyses, a theoretical treatment has been developed based on nucleation stress and energy criteria which predicts a “barrierless” nucleation process exists even at low misfits (< 1%). Accordingly, the observed misfit dislocation nucleation event has been found both experimentally and theoretically to be rate-controlled solely by Peierls barrier dependent, glide-activated processes with activation energies of ∼2 eV.

Influence of in volatilization on photoluminescence in InGaN/GaN multiple quantum wells

2021 ◽  
Vol 11 (12) ◽  
pp. 2033-2038
Author(s):  
Kaiju Shi ◽  
Chengxin Wang ◽  
Rui Li ◽  
Shangda Qu ◽  
Zonghao Wu ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Internal Quantum Efficiency ◽  
Excitation Power ◽  
Localized States ◽  
Multiple Quantum ◽  
High Excitation ◽  
Rich Phase ◽  
Pl Spectra ◽  
Localization Effect ◽  
Effect Of Structure

Two multiple quantum well (MQW) InGaN/GaN structures emitting green light, without (A) and with (B) an indium (In) volatilization suppression technique (IVST) during growth of the active region, were fabricated. The dependencies of the photoluminescence (PL) spectra upon temperature at different levels of excitation power were investigated. The results indicate that an IVST can increase the In content while suppressing the phase separation caused by volatilization of that In incorporated in the well layers. Also, compared with Structure B with IVST, which contains one phase structure, Structure A without IVST, which contains two separate phases (i.e., an In-rich phase and an In-poor phase), exhibits higher internal quantum efficiency (IQE) at low excitation power and lower IQE at high excitation power. The former is mainly attributed to the stronger In-rich phase-related localization effect of Structure A, because the In-rich phase-related emission dominates the PL spectra of Structure A at a low excitation power; the latter is mainly due to the In-poor phase-related weaker localization effect of Structure A, because the In-poor phase-related emission dominates the PL spectra of Structure A at high excitation power because localized states in this In-rich phase are saturated.

Integrated Rib Waveguide-Photodetector Using Si/Si1−xGex Multiple Quantum Wells for Long Wavelenghts

1991 ◽  
Vol 220 ◽  
Author(s):  
V. P. Kesan ◽  
P. G. May ◽  
G. V. Treyz ◽  
E. Bassous ◽  
S. S. Iyer ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Internal Quantum Efficiency ◽  
Optical Quality ◽  
Silicon Substrates ◽  
Multiple Quantum ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Long Wavelength ◽  
Response Bandwidth ◽  
Soi Substrates

ABSTRACTWe have investigated the structural, electrical, and optical quality of epitaxial Si and Si1−xGex films grown by MBE on SIMOX (Separation by IMplanted OXygen) silicon substrates. Epitaxial films grown on these SOI substrates have been characterized using planar and cross-sectional TEM, high resolution X-ray diffraction, SIMS, and Seeco chemical etching to delineate defects. We have fabricated Si/SiGe P-i-N photodetectors integrated with Si waveguides on SOI for long wavelength applications. Low reverse leakage current densities were seen in these device structures. The photodetector exhibited an internal quantum efficiency of 50% at 1.1 μm with a frequency response bandwidth of 2 GHz.

Temperature Dependence of Cathodoluminescence From InxGa1-xAs/GaAs Multiple Quantum Wells

1995 ◽  
Vol 379 ◽  
Author(s):  
K. Rammohan ◽  
D.H. Rich ◽  
A. Larsson
Keyword(s):  
Activation Energy ◽  
Quantum Wells ◽  
Temperature Dependence ◽  
Spatial Variations ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Nonradiative Recombination ◽  
Intensity Dependence ◽  
Thermally Activated

ABSTRACTThe temperature dependence of the cathodoluminescence (CL) originating from In0.21Ga0.79As/GaAs multiple quantum wells has been studied between 86 and 250 K. The CL intensity exhibits an Arrenhius-type dependence on temperature (T), characterized by two different activation energies. The spatial variations in activation energy caused by the presence of interfacial misfit dislocations is examined. The CL intensity dependence on temperature for T ≲ 150 K is controlled by thermally activated nonradiative recombination. For T ≳ 150 K the decrease in CL intensity is largely influenced by thermal re-emission of carriers out of the quantum wells.

The Roles of Stress, Geometry and Orientation on Misfit Dislocations Kinetics and Energetics in Epitaxial Strained Layers.

1991 ◽  
Vol 239 ◽  
Author(s):  
R. Hull ◽  
J. C. Bean ◽  
F. Ross ◽  
D. Bahnck ◽  
L. J. Pencolas
Keyword(s):  
Misfit Dislocation ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Slip Systems ◽  
Strained Layers ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Strain Stress ◽  
Kinetics Of

ABSTRACTThe geometries, microstructures, energetics and kinetics of misfit dislocations as functions of surface orientation and the magnitude of strain/stress are investigated experimentally and theoretically. Examples are drawn from (100), (110) and (111) surfaces and from the GexSi1–x/Si and InxGa1–x/GaAs systems. It is shown that the misfit dislocation geometries and microstructures at lattice mismatch stresses < - 1GPa may in general be predicted by operation of the minimum magnitude Burgers vector slipping on the widest spaced planes. At stresses of the order several GPa, however, new dislocation systems may become operative with either modified Burgers vectors or slip systems. Dissociation of totál misfit dislocations into partial dislocations is found to play a crucial role in strain relaxation, on surfaces other than (100) under compressive stress.

Sign in / Sign up

Export Citation Format

Share Document