Shape and spatial correlation control of InAs-InAlAs-InP(001) nanostructure superlattices

The control of shape and spatial correlation of InAs-InAlAs-InP(001) nanostructure superlattices has been realized by changing the As overpressure during the molecular-beam epitaxy (MBE) growth of InAs layers. InAs quantum wires (QWRs) are obtained under higher As overpressure (1x10(-5) Torr), while elongated InAs quantum dots (QDs) are formed under lower As overpressure (5x10(-6) or 2.5x10(-6) Torr). Correspondingly, spatial correlation changes from vertical anti-correlation in QWR superlattices to vertical correlation in QD superlattices, which is well explained by the different alloy phase separation in InAlAs spacer layers triggered by the InAs nanostrcutures. It was observed that the alloy phase separation in QD superlattices could extend a long distance along the growth direction, indicating the vertical correlation of QD superlattices can be kept in a wide range of spacer layer thickness.

Interband and intraband photocurrent of self-assembled InAs/InAlAs/InP nanostructures

The interband and intraband photocurrent properties of InAs/InAlAs/InP nanostructures have been studied. The doping effect on the photoluminescence properties of the quantum dots and the anisotropy of the quantum wire interband photocurrent properties are presented and discussed. With the help of interband excitation, an intraband photocurrent signal of the InAs nanostructures is observed. With the increase of the interband excitation power, the intraband photocurrent signal first increases and then decreases, which can be explained by the variance of the ground state occupation of the InAs nanostructures and the change of the mobility and lifetime of the electrons. The temperature dependence of the intraband photocurrent signal of the InAs nanostructures is also investigated.

Optical properties of self-assembled InAs/InAlAs/InP quantum wires with different InAs deposited thickness

We report on the photoluminescence (PL) properties of InAs/InAlAs/InP quantum wires (QWRs) with various InAs deposited thickness. The PL linewidth of the QWRs decreases with increasing InAs deposited thickness due to the different thicknesses of the QWRs and defects in the samples. The defects and lateral composition modulation of the InAlAs layers play an important role in the temperature-dependent PL properties of the samples. (c) 2005 Elsevier B.V. All rights reserved.

Symmetry in the diagonal self-assembled InAs quantum wire arrays on InP substrate

Diagonal self-assembled InAs quantum wire (QWR) arrays with the stacked InAs/In0.52Al0.48As structure are grown on InP substrates, which are (001)-oriented and misoriented by 6degrees towards the [100] direction. Both the molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE) techniques are employed. Transmission electron microscopy reveals that whether a diagonal InAs QWR array of the stacked InAs/InAlAs is symmetrical about the growth direction or not depends on the growth method as well as substrate orientation. Asymmetry in the diagonal MEE-grown InAs QWR array can be ascribed to the influence of surface reconstruction on upward migration of adatoms during the self-assembly of the InAs quantum wires.

Strain relaxation of InP film directly grown on GaAs patterned compliant substrate

In order to overcome the large lattice mismatch in the heteroepitaxy, a new patterned compliant substrate method has been introduced, which has overcome the disadvantages of previously published methods. InP film of thickness 800 nm was directly grown on this substrate. Scanning electron microscopy (SEM) has shown that good surface morphology has been obtained. In addition, Photoluminescence (PL) and double crystal X-ray diffraction (DCXRD) study have shown that the residual strain has been reduced, and that the structure quality has been improved. (C) 2002 Elsevier Science B.V. All rights reserved.

Study on pollution for the photoelectronic material InP

The mass spectrum analysis of crystal face (100) and (111) and the photoluminescence analysis of crystal face (100) in the photoelectronic material InP were given. The Hall coefficient, charge carrier concentration and Hall mobility were determined. Experimental results indicate that the pollution of silicon is predominant.

Influence of growth conditions on self-assembled InAs nanostructures grown on (001)InP substrate by molecular beam epitaxy

Self-assembled InAs nanostructures on (0 0 1) InP substrate have been grown by molecular beam epitaxy (MBE) and evaluated by transmission electron microscopy (TEM) and photoluminescence (PL). It is found that the morphologies and PL properties of InAs nanostructures depend strongly on the growth condition. For the same buffer layer, elongated InAs quantum wires (QWRs) and no isotropic InAs quantum dots (QDs) can be obtained using different growth conditions. At the same time, for InAs quantum dots, PL spectra also show several emission peaks related to different islands size. Theoretical calculation indicated that there are size quantization effects in InAs islands. (C) 2001 Elsevier Science B.V. All rights reserved.

InAs self-assembled quantum dots grown on an InP (311)B substrate by molecular beam epitaxy

Self-assembled InAs quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on a (311)B InP substrate. Transmission electron microscopy clearly shows that a high density of smaller InAs islands can be obtained by using such a high index substrate. After introducing a lattice-matched underlying In0.52Al0.24Ga0.24As layer, the InAs QDs are much more uniform in size and form two-dimensional well ordered arrays. The photoluminescence (PL) spectra also confirm that the InAs QDs grown on underlying In0.52Al0.24Ga0.24As have a better quality than those grown in the In0.52Al0.48As matrix. A simple calculation indicates that the redshift of the PL peak energy mainly results from InAs QDs on underlying In0.52Al0.24Ga0.24As of large size. (C) 2001 American Institute of Physics.

Impurity-free vacancy diffusion technique for InGaAsP/InP multiple quantum well laser structure

Bandgap tuning of the InGaAsP/InP multiple quant um well (MQW) laser structure by the impurity-free vacancy diffusion (IFVD) is investigated using photoluminescence. It has been demonstrated that the effects of the plasma bombardment to the:sample surface involved in the IFVD technique can enhance the intermixing of the InGaAsP/InP MQW laser structure. The reliability of the IFVD technique, particularly the effects of the surface decomposition and the intrinsic defects formed in the growth or preparation of the wafer, has been discussed.

Defects and morphologies in In0.8Ga0.2As/InAlAs/InP(001) for high electron-mobility transistors

Defects and morphologies are presented in this paper as revealed with transmission electron microscope (TEM) in the In(0.8)G(0.2)As/InAlAs heterostructure on InP(001) for high-electron-mobility transistors application. Most of the misfit dislocation lines are 60 degrees type and they deviate < 110 > at some angles to either side according to their Burges vectors. The misfit dislocation lines deviating [-110] are divided into two types according to whether their edge component b(eg) of Burges vectors in [001] pointing up or down. If b(eg) points up in the growth direction, there is the local periodical strain modulation along the dislocation line. In addition, the periodical modulation in height along [-110] on the In(0.8)G(0.2)As surface is observed, this surface morphology is not associated with the relaxation of mismatch strain.

The effect of substrate orientation on the morphology of InAs nanostructures on (001) and (11n)A/B(n=1-5) InP substrates

Strained InAs nanostructures have been grown by solid-source molecular beam epitaxy in In0.52Al0.48As matrix on different InP substrate surfaces ((0 0 1) and (1 1 n)A/B (n = 1 - 5)). The morphology of the nanostructures was characterized using atomic force microscopy (AFM). The AFM results reveal interesting differences in the size, shape, and alignment of the nanostructures between different oriented surfaces. It was found that some faceted nanostructures tend to form on A-type surfaces, the shape and the alignment of these nanostructures show clear dependence on the substrate orientation. Samples grown on (0 0 1) and B-type surfaces showed preferentially dense round dots. Dots formed on (1 1 3)B, (1 1 3)B and (1 1 5)B surfaces have a higher dot density and size homogeneity, which shows a potential for the production of high-quality and customized self-assembled quantum dots for photonics applications. (C) 2000 Elsevier Science B.V. All rights reserved.

Room temperature 1.55 mu m emission from InAs quantum dots grown on (001)InP substrate by molecular beam epitaxy

Self-assembled InAs nanostructures on (0 0 1)InP substrate have been grown by molecular beam epitaxy (MBE) and evaluated by transmission electron microscopy (TEM) and photoluminescence (PL). It is found that the morphologies of InAs nanostructures depend strongly on the underlying alloy. Through introducing a lattice-matched underlying InAlGaAs layer on InAlAs buffer layer, the InAs quantum dots (QDs) can be much more uniform in size and great improvement in PL properties can be attained at the same time. In particular, 1.55 mu m luminescence at room temperature (RT) can be realized in InAs QDs deposited on (0 0 1)InP substrate with underlying InAlGaAs layer. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Two-dimensional ordering of self-assembled InAs quantum dots grown on (311)B InP substrate

Self-assembled InAs quantum dots (QDs) in InAlAs grown on (001) and (311)B InP substrates by molecular beam epitaxy (MBE) have been comparatively investigated. A correlated study of atomic force microscopy (AFM) and photoluminescence (PL) disclosed that InAs QDs grown on high-index InP substrates can lead to high density and uniformity. By introducing a lattice-matched InAlGaAs overlayer on InAlAs buffer, still more dense and uniform InAs QDs were obtained in comparison with InAs QDs formed with only InAlAs matrix. Moreover, two-dimensional well-ordered InAs dots with regular shape grown on (311)B InP substrates are reported for the first time. We explained this exceptional phenomenon from strain energy combined with kinetics point of view. (C) 2000 Elsevier Science B.V. All rights reserved.

Self-assembled InAs quantum wires on InP(001)

Self-assembled InAs quantum wires (QWRs) embedded in In0.52Al0.48As, In0.53Ga0.47As, and (In0.52Al0.48As)(n)/(In0.53Ga0.47As)(m)-short-period-lattice matrices on InP(001) were fabricated with molecular beam epitaxy (MBE). These QWR lines are along [110], x 4 direction in the 2 x 4 reconstructed (001) surface as revealed with reflection high-energy electron diffraction (RHEED). Alignment of quantum wires in different layers in the InAs/spacer multilayer structures depends on the composition of spacer layers. (C) 2000 Elsevier Science B.V. All rights reserved.