An investigation of the crystalline nature for GaSb films on Si(111) at varied growth temperature and growth rate

The single crystalline III-V films on substrates such as silicon and germanium are preferred by researchers to enhance the performance of a MOSFET or CMOS. In this study, we investigated the possible factors responsible for generating twin crystal growth for III-antimonides, especially GaSb grown on Si(111). We tested several base templates such as Si(111)-√3 × √3-Ga, Si(111)-√3 × √3-In, Si(111)-direct, and we have varied the growth conditions through varying the substrate temperature and growth rate. The molecular beam epitaxy growth method was used to deposit GaSb films. Our results reflect that in absence of an initial layer of GaSb film grown at a low substrate temperature, the anti-phase domains and defect densities cannot be reduced which results in the formation of twin crystal. We found that the high substrate temperature during the growth is the deciding factor in generating twin crystal growth.

Source:IOPscience

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Study of hydrogen implantation-induced blistering in GaSb for potential layer transfer applications

GaSb samples were implanted by 100 keV hydrogen ions (H+) at room temperature with fluence values of 1  ×  1017 and 2  ×  1017 ions cm−2. Post-implantation annealing studies revealed that the samples implanted with a fluence of 2  ×  1017 ions cm−2 did not show blistering/exfoliation. For the lower fluence, the samples showed the formation of surface blisters/craters along with the large area exfoliation of the top H-implanted surface. Topographical investigations of the samples were carried out using Nomarski optical microscopy, atomic force microscopy and stylus surface profilometry. The lateral sizes and heights of the blisters varied between 2–5 µm and 5–20 nm respectively. The root mean square roughness of the exfoliated region was about 12 nm while the exfoliation depth was found to be 730 nm. The exfoliation depth in the H-implanted GaSb is close to the damage concentration peak as found from SRIM calculations. The Föppl–von Karman theory of thin plates has been used to understand the effect of internal pressure and stress on the surface blistering. Using the above mentioned implantation and annealing parameters, potential layer transfer of GaSb could be enabled.

Source:IOPscience

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X-ray scattering from epitaxial GaSb/InAs thin films below and above the critical thickness

The structure of layers of GaSb grown on InAs substrates has been investigated by means of high-resolution x-ray diffraction. The samples were grown in Oxford using the metal–organic vapour phase epitaxy facility to produce high-quality single-crystal layers with thicknesses between 60 and 3000 Å. The x-ray scattering experiments were performed with a Philips MRD diffractometer in Oxford and with the XMaS facility at the ESRF. The results show that the scattering for layers with a thickness below Tc' ~ 1250 Å is different from the scattering for those with larger thicknesses. The scattering from the thinner layers shows that the in-plane lattice constant of the GaSb is very close to that of the InAs substrate and that the strain does not vary through the film, while the measured diffuse scattering is in good agreement with calculations of the scattering from isolated 60o dislocations. The thicker layers show no diffuse scattering but single-Gaussian Bragg peaks and the scattering is that expected from a mosaic layer with a large concentration of 60o dislocations. Analysis of the peak parameters shows that the average in-plane lattice constant is intermediate between those of bulk GaSb and bulk InAs and that there is a changing strain through the film. The critical thickness Tc for GaSb on InAs is calculated as about 204 Å. We argue that between 204 and 1250 Å there are only a few dislocations, but thicker films are relaxed by spontaneous creation of a dislocation network. The results demonstrate the power of high-resolution x-ray scattering for studying non-destructively the structures of thin films containing dislocations, and show that there is a marked change in the scattering for layers above the critical thicknesses Tc and Tc'.

Source:IOPscience

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Growth of self-assembled PbSe quantum-dots on GaSb(100) by liquid phase epitaxy

Self-assembled PbSe quantum-dots (QD) have been grown on GaSb(100) substrates from the liquid phase. A Pb-rich melt at 517°C was used with 10°C supercooling and with a short (10 ms) melt-substrate contact time. Atomic force microscopy has revealed that the PbSe QDs are 4–10 nm in height and 10–40 nm in diameter, with an area density of 1.7×1010 cm−2. The growth of QDs occurs in the Volmer–Weber mode and is a result of the difference in lattice structures between the PbSe and GaSb rather than the lattice constants.

Source:IOPscience

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