The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices

AbstractThe nature and origin of lateral composition modulations in (AlAs)m(InAs)n short-period strained-layer superlattices grown by molecular beam epitaxy on InP substrates have been investigated by x-ray diffraction, atomic force microscopy, and transmission electron microscopy. Strong modulations were observed for growth temperatures between ≈ 540 and 560° C. The maximum strength of modulations was found for SPS samples with InAs mole fraction x (= n/(n+m)) close to ≈ 0.50 and when n ≈ m ≈ 2. The modulations were suppressed at both high and low values of x. For x > 0.52 (global compression), the modulations were along the <100> directions in the (001) growth plane. For x < 0.52 (global tension), the modulations were along the two <310> directions rotated ≈ ±27° from [110] in the growth plane. The remarkably constant wavelength of the modulations, between ≈ 20–30 nm, and the different modulation directions observed, suggest that the origin of the modulations is due to surface roughening associated with the high misfit between the individual SPS layers and the InP substrate. Highly uniform unidirectional modulations have been grown by control of the InAs mole fraction and growth on suitably offcut substrates, which show great promise for application in device structures.

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Transmission electron microscopy of short‐period Si/Ge strained‐layer superlattices on Ge substrates

Applied Physics Letters ◽

10.1063/1.101871 ◽

1989 ◽

Vol 55 (5) ◽

pp. 448-450 ◽

Cited By ~ 32

Author(s):

W. Wegscheider ◽

K. Eberl ◽

H. Cerva ◽

H. Oppolzer

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Strained Layer ◽

Transmission Electron ◽

Short Period ◽

Strained Layer Superlattices

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New Relaxation Mechanism in Short Period Si/Ge Strained-Layer Superlattices

MRS Proceedings ◽

10.1557/proc-183-155 ◽

1990 ◽

Vol 183 ◽

Cited By ~ 3

Author(s):

Werner Wegscheider ◽

Karl Eberl ◽

Gerhard Abstreiter ◽

Hans Cerva ◽

Helmut Oppolzer

Keyword(s):

Activation Barrier ◽

Relaxation Mechanism ◽

Layer Growth ◽

Lattice Imaging ◽

Strained Layer ◽

Partial Dislocations ◽

Transmission Electron ◽

Short Period ◽

Strained Layer Superlattices ◽

First Time

AbstractHigh quality Si/Ge strained-layer superlattices composed of a sequence of alternating 3 monolayers pure Si and 9 monolayers pure Ge have been grown by molecular beam epitaxy at 310°C on Ge(001) substrates. In order to investigate the transition from coherent to incoherent growth in these tensily strained structures a set of samples with varying number of superlattice periods has been studied by transmission electron microscopy. It is found that superlattices as thick as 33 nm at least show perfect and defect-free layer growth whereas for thicker superlattices strain accommodation occurs. For this strained heteroepitaxial system we observed, to our knowledge, for the first time the formation of microtwins as the only relaxation mechanism. High-resolution lattice imaging reveals that the twin lamellae result from successive glide of 90° (a/6)<112> Shockley partial dislocations on adjacent {111} planes from the surface towards the bulk. The activation barrier which has to be overcome in the case of 90° partial dislocations is compared with the energies required for the nucleation of 60° perfect and 30° partial misfit dislocation half-loops.

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Optical studies of InAs/GaAs on GaAs short-period strained-layer superlattices grown by MBE and MEE

Journal of Crystal Growth ◽

10.1016/0022-0248(91)91006-v ◽

1991 ◽

Vol 111 (1-4) ◽

pp. 388-392 ◽

Cited By ~ 7

Author(s):

T.C. Hasenberg ◽

D.S. McCallum ◽

X.R. Huang ◽

A.L. Smirl ◽

M.D. Dawson ◽

...

Keyword(s):

Optical Studies ◽

Strained Layer ◽

Short Period ◽

Strained Layer Superlattices

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Realization of Short Period SI/GE Strained-Layer Superlattices

Heterostructures on Silicon: One Step Further with Silicon ◽

10.1007/978-94-009-0913-7_18 ◽

1989 ◽

pp. 153-160 ◽

Cited By ~ 3

Author(s):

K. Eberl ◽

W. Wegscheider ◽

E. Friess ◽

G. Abstreiter

Keyword(s):

Strained Layer ◽

Short Period ◽

Strained Layer Superlattices

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Characterization of the interface of ZnSe-ZnS strained-layer superlattices by MeV transmission electron microscopy and ion-channeling

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/0168-583x(88)90640-4 ◽

1988 ◽

Vol 33 (1-4) ◽

pp. 603-606 ◽

Cited By ~ 10

Author(s):

Kawakami Yoichi ◽

Taguchi Tsunemasa ◽

Satou Mamoru ◽

Hiraki Akio

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Strained Layer ◽

Ion Channeling ◽

Transmission Electron ◽

Strained Layer Superlattices

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Low-pressure metallorganic vapor-phase epitaxy (LP-MOVPE) growth and characterization of short-period strained-layer superlattices (SPSLSs) on InP substrates

10.1117/12.175778 ◽

1994 ◽

Author(s):

A. Lindner ◽

Q. Liu ◽

F. Scheffer ◽

W. Prost ◽

Franz-Josef Tegude

Keyword(s):

Vapor Phase ◽

Low Pressure ◽

Vapor Phase Epitaxy ◽

Strained Layer ◽

Short Period ◽

Movpe Growth ◽

Strained Layer Superlattices ◽

Inp Substrates

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Study of Photovoltaic Devices with Hybrid Active Layer

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.293.51 ◽

2019 ◽

Vol 293 ◽

pp. 51-64

Author(s):

Pawel Jarka ◽

Tomasz Tański ◽

Bartlomiej Hrapkowicz ◽

Barbara Hajduk ◽

Kamil Bystroń ◽

...

Keyword(s):

Optical Properties ◽

Bulk Heterojunction ◽

Photovoltaic Cells ◽

Deposition Process ◽

Thin Layers ◽

Force Microscopy ◽

Active Layers ◽

Transmission Electron ◽

Current Voltage ◽

The Individual

The aim of this work is to present the influences of composition of the material and manufacturing technology conditions of the organic photovoltaics devices (OPv) with the organic and hybrid bulk heterojunction on the active layers properties and cells performance. The layers were produced by using small molecular compounds: the metal-phthalocyanine (MePc) and perylene derivatives (PTCDA) and the titanium dioxide (TiO2) nanoparticles. Two kinds of metal phthalocyanines (NiPc, TiOPc) were used as donor material and pperylenetetracarboxylic dianhydride (PTCDA) as an acceptor. The used manufacturing technique allowed to employ thin layers of materials in a fast deposition process. Bulk heterojunction was created by simultaneously applying the MePc:PTCDA materials during the evaporation of the components mixture.The research was based on the estimate of composition of bulk heterojunction, the examination of the surface morphology of the used layers and optical properties studies of the heterojunction and its implementation to photovoltaic architecture. The produced photovoltaic cells parameters were determined on the basis of current - voltage characteristics.The researches of structure of obtained layers were conducted by using scanning electron microscope (SEM) and transmission electron microscopy (TEM). The quantitative determination of surface topography by determining RMS and Ra coefficients were performed by atomic force microscopy (AFM). In order to determine the optical properties of the films the UV-Visible spectroscope have been utilized. Current - voltage characteristics were employed to determine the basic photovoltaic parameters using a dedicated device.The paper describes the influence of the individual components sharing the bulk heterojunction on its structure, optical properties and morphology of surface. In addition it allows for linking active layers properties with the parameters of the photovoltaic cells. The obtained results suggest the possibility of developing the utilized materials and technology in the further works on photovoltaic structures.

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