Photoluminescence Investigations of High Purity Mbe-Grown Sil−xGex/Si Single Quantum Wells

1993 ◽  
Vol 298 ◽  
Author(s):  
M. Wachter ◽  
F. Schdffler ◽  
K. Thonke ◽  
R. Sauer ◽  
H.-J. Herzog ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Strain Energy ◽  
Free Exciton ◽  
Sige Layer ◽  
Band Edge ◽  
Background Concentration ◽  
Single Quantum ◽  
Single Quantum Well ◽  
Cap Layer ◽  
Shallow Impurities

AbstractSil-xGex/Si(100) single quantum well samples were grown by MBE with x varying from 18.5% to 36%, well widths Lz from 1.1 nm to 175 nm, and growth temperatures To in the range from 350°C to 750°C. We studied the photoluminescence (PL) properties in detail using Fourier transform spectroscopy. In most of the samples, the dominant and phononresolved SiGe band edge PL exhibits exclusively free exciton luminescence even at sample temperatures as low as 2 K. From the absence of bound excitons we conclude that the background concentration of shallow impurities is low in our SiGe layers. Variation of the growth temperature of the Si cap layer strongly influences the efficiency of the SiGe band edge PL at higher temperatures, whereas the PL efficiency is less affected at T=4 K. This indicates a reduction of the concentration of non-radiative defects in the cap layer when it is grown at higher temperatures. A broad PL band 150 meV below the SiGe bandgap, supposed to be typical for MBE-grown material, is weakly observed in only a few samples. The strength of the broad PL band does not unambiguously depend on the strain energy density in the SiGe layer as recently suggested.

Spontaneous Lateral Modulations in InAlAs Buffer Layers Grown by MBE on InP Substrates

1995 ◽  
Vol 417 ◽  
Author(s):  
F. Peiró ◽  
A. Cornet ◽  
J. C. Ferrer ◽  
J. R. Morante ◽  
G. Halkias ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Single Quantum ◽  
X Ray Diffraction ◽  
Single Quantum Well ◽  
Quantum Well Structures ◽  
X Ray ◽  
Transmission Electron ◽  
Inp Substrates

AbstractTransmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) have been used to analyze the spontaneous appearance of lateral composition modulations in InyAl1−yAs (yIn.≅ 50%) buffer layers of single quantum well structures grown by molecular beam epitaxy on exact and vicinal (100) InP substrates, at growth temperatures in the range of 530°C–580°C. The influence of the growth temperature, substrate misorientation and epilayer mismatch on the InAlAs lateral modulation is discussed. The development of a self-induced quantum-wire like morphology in the In0.53Ga0.47As single quantum wells grown over the modulated buffers is also commented on.

Grazing Incidence X-Ray Scattering Studies of Single Quantum Wells

1987 ◽  
Vol 31 ◽  
pp. 155-160
Author(s):  
S. Bates ◽  
P.D. Hatton ◽  
C.A. Lucas ◽  
T.W. Ryan ◽  
S.J. Miles ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Lattice Mismatch ◽  
Thick Layer ◽  
Grazing Incidence ◽  
Single Quantum ◽  
Individual Layer ◽  
Single Quantum Well ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractX-ray scattering techniques at grazing incidence have been used to characterize single quantum well hetero–structures. Double–and triple-axis diffractometry has been used to determine lattice mismatch and layer thickness of a 250Å thick layer of AlInAs grown by MBE on an InP substrate and capped by a 45Å GaAs layer. Reflectivity measurements in the triple – crystal mode permit accurate measurement of individual layer thicknesses, relative electron density and interface roughnesses on the Angstrom level.

INSIGHTS ON THE BOUND STATES IN THE STRAINED CdSe–ZnSe SINGLE-QUANTUM WELLS

2008 ◽  
Vol 22 (13) ◽  
pp. 2055-2069 ◽  
Author(s):  
NACIR TIT ◽  
IHAB M. OBAIDAT
Keyword(s):  
Quantum Wells ◽  
Valence Band ◽  
Quantum Confinement ◽  
Bound States ◽  
Axial Strain ◽  
Bound State ◽  
Band Offset ◽  
Single Quantum ◽  
Valence Band Offset ◽  
Single Quantum Well

The bound states in the (CdSe) Nw– ZnSe (001) single quantum well are investigated versus the well width (Nw monolayers) and the valence-band offset (VBO). The calculation, based on the sp3s* tight-binding method which includes the spin-orbit interactions, is employed to calculate the band-gap energy (Eg), quantum-confinement energy (EQ), and band structures. It is found that the studied systems possess a vanishing valence-band offset ( VBO ≃ 0) in consistency with the common-anion rule, and a large conduction band offset of about ( CBO ≃ 1 eV ); both of which made the electronic confinement become predominant. The bi-axial strain, on the other hand, remains to control the hole states. Namely, the two highest (spin-degenerate) hole states are found to localize at the two interfaces due to the formation of two similar strain-induced potential dips at these interfaces, each of depth equal to the strain energy ~35 meV. More importantly, the ultrathin CdSe wells (with Nw ≤ 4 monolayers) are found to contain only a single (spin-degenerate) bound state; but by increasing the well width further, a new (spin-degenerate) bound state falls into the well every time Nw hits a multiple of 4 monolayers (more specifically, for 4n+1 ≤ Nw ≤ 4 (n+1), the number of bound states is (n+1), where n is an integer). The rule governing the variation of the quantum-confinement energy EQ versus the well width Nw has been derived. Our theoretical results are in excellent agreement with the available experimental photoluminescence data.

Low Temperature Growth of Gaas Quantum Well Lasers by Modulated Beam Epitaxy

1991 ◽  
Vol 228 ◽  
Author(s):  
S. Xin ◽  
K. F. Longenbach ◽  
C. Schwartz ◽  
Y. Jiang ◽  
W. I. Wang
Keyword(s):  
Low Temperature ◽  
Quantum Well ◽  
Substrate Temperature ◽  
Quantum Wells ◽  
High Growth ◽  
Quantum Well Lasers ◽  
Single Quantum ◽  
Single Quantum Well ◽  
Temperature Growth ◽  
Low Temperature Growth

ABSTRACTGaAs single quantum well lasers have been successfully grown at low temperatures by a modulated beam epitaxy process in which the Al/Ga flux is held constant while the As flux is periodically shut off to produce a metal-rich surface. Devices grown at a substrate temperature of 500 °C exhibit threshold current densities below 1 kA/cm2. This value is lower than normally grown low temperature lasers and is the lowest achieved by any low substrate temperature growth technique. In addition, low temperature (10 K) photoluminescence of single quantum wells grown with this technique exhibit full-width half maximum values, comparable to that attainable by higher temperature growth techniques. The improved quality of these low temperature grown quantum structures is attributed to both a smoothing of the growth front and a reduction of excess As during the modulated beam epitaxy process. The high growth rates and less frequent shutter operation of this technique make it a more practical than migration enhanced epitaxy or atomic layer epitaxy for low temperature growth.

Effects of interdiffusion on the sub‐band‐edge structure of In0.53Ga0.47As/InP single quantum wells

1993 ◽  
Vol 73 (11) ◽  
pp. 7524-7532 ◽  
Author(s):  
Joseph Micallef ◽  
E. Herbert Li ◽  
Bernard L. Weiss
Keyword(s):  
Quantum Wells ◽  
Band Edge ◽  
Single Quantum ◽  
Edge Structure
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