Normal‐incidence strained‐layer superlattice Ge0.5Si0.5/Si photodiodes near 1.3 μm

ABSTRACTPowerful mathematical tools have made it possible to simulate the optical spectra of strained layer superlattices. The results of these calculations are compared to experimental ones obtained on ZnS-ZnSe SLSs. The photoluminescence spectra is dominated by a single major peak with a long asymmetrical tail end or a secondary peak at lower energies. This secondary peak or tail end is attributed to the disorder within the superlattice. The PL spectra is simulated using a novel model based on the following parameters; the free exciton energy, the strain/stress state between the lattice constants, the probability of an occurrence of a dislocation, the probability that the dislocation generates and propagates and the critical thickness. The reflectivity simulation is also novel and is based on an impedance in a spatial dispersion model. It is essential to consider the strain that is induced in the SL, when the dielectric constant is dependent on the variation of the frequency near the fundamental transition energies. As a result only normal incidence is considered.

Download Full-text

The limits of strain and lattice parameter measurements by CBED

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154561 ◽

1989 ◽

Vol 47 ◽

pp. 518-519

Author(s):

Hamish L. Fraser

Keyword(s):

Electron Beam ◽

Mirror Symmetry ◽

Local Symmetry ◽

Lattice Parameter ◽

Growth Direction ◽

Surface Relaxation ◽

Strained Layer ◽

Axis Parallel ◽

Local Lattice ◽

Strained Layer Superlattice

The topic of strain and lattice parameter measurements using CBED is discussed by reference to several examples. In this paper, only one of these examples is referenced because of the limitation of length. In this technique, scattering in the higher order Laue zones is used to determine local lattice parameters. Work (e.g. 1) has concentrated on a model strained-layer superlattice, namely Si/Gex-Si1-x. In bulk samples, the strain is expected to be tetragonal in nature with the unique axis parallel to [100], the growth direction. When CBED patterns are recorded from the alloy epi-layers, the symmetries exhibited by the patterns are not tetragonal, but are in fact distorted from this to lower symmetries. The spatial variation of the distortion close to a strained-layer interface has been assessed. This is most readily noted by consideration of Fig. 1(a-c), which show enlargements of CBED patterns for various locations and compositions of Ge. Thus, Fig. 1(a) was obtained with the electron beam positioned in the center of a 5Ge epilayer and the distortion is consistent with an orthorhombic distortion. When the beam is situated at about 150 nm from the interface, the same part of the CBED pattern is shown in Fig. 1(b); clearly, the symmetry exhibited by the mirror planes in Fig. 1 is broken. Finally, when the electron beam is positioned in the center of a 10Ge epilayer, the CBED pattern yields the result shown in Fig. 1(c). In this case, the break in the mirror symmetry is independent of distance form the heterointerface, as might be expected from the increase in the mismatch between 5 and 10%Ge, i.e. 0.2 to 0.4%, respectively. From computer simulation, Fig.2, the apparent monocline distortion corresponding to the 5Ge epilayer is quantified as a100 = 0.5443 nm, a010 = 0.5429 nm and a001 = 0.5440 nm (all ± 0.0001 nm), and α = β = 90°, γ = 89.96 ± 0.02°. These local symmetry changes are most likely due to surface relaxation phenomena.

Download Full-text

Optical and structural characteristics of InGaAs/GaAs strained-layer superlattice

10.1117/12.318274 ◽

1998 ◽

Author(s):

Mei Li ◽

Xueqian Li ◽

Xiaowei Song ◽

Zhongjiu Ge ◽

Xingde Zhang

Keyword(s):

Structural Characteristics ◽

Strained Layer ◽

Strained Layer Superlattice

Download Full-text

Growth of a novel InAs‐GaAs strained layer superlattice on InP

Applied Physics Letters ◽

10.1063/1.95542 ◽

1985 ◽

Vol 46 (6) ◽

pp. 569-571 ◽

Cited By ~ 58

Author(s):

M. C. Tamargo ◽

R. Hull ◽

L. H. Greene ◽

J. R. Hayes ◽

A. Y. Cho

Keyword(s):

Strained Layer ◽

Strained Layer Superlattice

Download Full-text

On the Existence of Multiple Equilibrium States in Strained-Layer Superlattices

MRS Proceedings ◽

10.1557/proc-103-61 ◽

1987 ◽

Vol 103 ◽

Cited By ~ 2

Author(s):

William C. Johnson

Keyword(s):

Free Energy ◽

Equilibrium State ◽

Stable Equilibrium ◽

Multiple Equilibrium ◽

Equilibrium Thermodynamic ◽

Relative Thickness ◽

Two Phase ◽

Strained Layer ◽

Strained Layer Superlattice ◽

Strained Layer Superlattices

ABSTRACTUsing recent results from the thermodynamics of stressed solids, two-phase coexistence in a simple binary strained-layer superlattice is examined. We show that for a given temperature and overall composition of the superlattice, there can exist more than one linearly stable, equilibrium thermodynamic state. That is, there may exist several combinations of relative thickness of the phases and corresponding phase compositions that minimize the free energy of the system. The equilibrium state observed experimentally can, therefore, be influenced by the processing path.

Download Full-text

High Spin Polarization of Conduction Band Electrons in GaAs-GaAsP Strained Layer Superlattice Fabricated as a Spin-Polarized Electron Source

Japanese Journal of Applied Physics ◽

10.1143/jjap.43.3371 ◽

2004 ◽

Vol 43 (6A) ◽

pp. 3371-3375 ◽

Cited By ~ 7

Author(s):

Tetsuya Matsuyama ◽

Hisaya Takikita ◽

Hiromichi Horinaka ◽

Kenji Wada ◽

Tsutomu Nakanishi ◽

...

Keyword(s):

Conduction Band ◽

Spin Polarization ◽

High Spin ◽

Electron Source ◽

Strained Layer ◽

Spin Polarized ◽

High Spin Polarization ◽

Strained Layer Superlattice

Download Full-text

Defect Reduction in GaAs Epilayers on Si Substrates Using Strained Layer Superlattices

MRS Proceedings ◽

10.1557/proc-91-99 ◽

1987 ◽

Vol 91 ◽

Cited By ~ 9

Author(s):

N. El-Masry ◽

N. Hamaguchi ◽

J.C.L. Tarn ◽

N. Karam ◽

T.P. Humphreys ◽

...

Keyword(s):

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Buffer Layers ◽

Threading Dislocations ◽

Defect Reduction ◽

Strained Layer ◽

Si Substrates ◽

Density Of Dislocations ◽

Strained Layer Superlattice ◽

Strained Layer Superlattices

ABSTRACTInxGa11-xAs-GaAsl-yPy strained layer superlattice buffer layers have been used to reduce threading dislocations in GaAs grown on Si substrates. However, for an initially high density of dislocations, the strained layer superlattice is not an effective filtering system. Consequently, the emergence of dislocations from the SLS propagate upwards into the GaAs epilayer. However, by employing thermal annealing or rapid thermal annealing, the number of dislocation impinging on the SLS can be significantly reduced. Indeed, this treatment greatly enhances the efficiency and usefulness of the SLS in reducing the number of threading dislocations.

Download Full-text