F. de Anda

High purity GaSb grown by LPE in a sapphire boat

Abstract GaSb layers grown by LPE in a sapphire boat exhibit higher free hole concentrations than layers grown at the same temperature but in a graphite boat. In both cases, as the growth temperature is lowered, the free hole concentration diminishes and eventually the layers’ conductivity change to N type. The transition temperature is lower for the samples grown in the sapphire boat. This behavior is explained assuming that the residual impurities coming from the graphite boat are mainly donors, making the concentration of the native acceptors less compensated in GaSb grown in the sapphire boat. The free carrier concentrations and their mobility were determined by infrared reflectivity. Evidence of the compensation effect was obtained from the photoluminescence spectra of the samples.

Growth of Quantum-Well Heterostructures by Liquid Phase Epitaxy

This work reviews the different techniques proposed and used to grow ultra-thin layers by Liquid Phase Epitaxy. Some of these approaches have allowed the production of quantum-well heterostructures for optoelectronic devices with performances comparable to devices made by Molecular Beam Epitaxy or Metal Organic Chemical Vapor Deposition.

AlGaAsSb and AlGaInAsSb Growth from Sb-rich Solutions

This work is related to the use of Sb as a solvent for the growth of antimony-based solid solutions by LPE. We have developed the growth technology of AlGaAsSb on GaSb substrates. A GaSb solid phase is eroded or melted back in contact with a saturated Al-Ga-As-Sb liquid due to the high non equilibrium degree on this system and the erosion increases with Al concentration. One of the techniques to diminish the erosion consists in increasing the initial supercooling but in this system, in the investigated area of compositions, it is impossible because of the low critical supercooling (ΔT cr ) of the liquid phase. We have conceived and developed a method to control ΔT cr by adding In to the liquid phase. It was found that when the In concentration increased the ΔT cr also increased. So the transition from the quaternary AlGaAsSb to the pentanary AlGaInAsSb allowed us to decrease the erosion process. This technique permits to grow high quality multilayer heterostructures based on antimonides.

Growth of low-etch-pit density InSb single crystals by the Czochralski method

Abstract InSb single crystals with an etch pit density of 3.8 × 10 2 cm −2 have been grown by the conventional Czochralski method. This low value has been obtained without “impurity hardening” by growing the crystals parallel to the (3 1 1) direction by imposing an axial temperature gradient and using the necking technique. Hall effect measurements show that the crystals have a carrier concentration of 2.8 × 10 16 cm −3 and a mobility of 62 835 cm 2 /V s at room temperature.

Temperature determination by solubility measurements and a study of evaporation of volatile components in LPE

Abstract When growing different structures by LPE it is necessary to know exactly the temperature on the boundary between the liquid and solid phases. That temperature can not be measured directly by a thermocouple because normally it is located at some distance from this boundary and in any LPE system there are always unknown temperature gradients. However the interface temperature and its distribution along the LPE boat can be determined by solubility measurements. The accuracy of such measurements will be affected by several factors and phenomena. One of such effects is related to the evaporation of volatile components. In this work we have used In–P liquid solutions and its phase diagram to determine the temperature distribution along an LPE boat and have also studied the effect of phosphorus evaporation. It is shown that phosphorus evaporation can be neglected for temperatures under 650°C but at higher temperatures it is significant.

Estimation of the instable composition areas and its dependence on the thickness of GalnAsSb layers grown on different substrates

In this work we inform about the results of estimations of the changes of the spinodal decomposition areas and its dependence on the thickness of epitaxial layers. The calculations have been performed using the CALPHAD method and the SGTE data taking into account the elastic energy generated by the lattice mismatch between forming solid solutions and substrate. We have shown that in thin layers the elastic energy may serve both as a stabilizing factor for compositions inside the immiscibility region but lattice matched, or close, to the substrate and, on the contrary, as a reason of instability for the compositions laying in the periphery of the miscible regions.

Lattice vibrations study of Ga1-xInxAsySb1-y quaternary alloys with low (In, As) content grown by liquid phase epitaxy

Raman scattering spectroscopy was used to measure and analyze the lattice vibrations in some quaternary Ga1−xInxAsySb1−y alloys with low (In, As) contents, (0.03 <x< 0.12 and 0.03 <y< 0.10). The layers were grown by liquid phase epitaxy on (001) GaSb substrates at 540°C. High Resolution X-Ray Diffraction results showed profiles associated with a quaternary layer lattice matched to the GaSb substrate as obtained from the (004) reflection. The experimental diffractograms were simulated to estimate alloy composition, thickness and lattice mismatch of the layer. Raman scattering results show phonon frequencies associated to the TO and LO GaAs-like modes as well as GaSb + InAs-like mode, which are characteristic of this quaternary alloy. The As content dependence of the phonon frequency measured in this alloy for low (In, As) contents agree well with the modified Random-Element Isodisplacement (REI) model and also with other available experimental reports. This method can also be used to estimate alloy compositions for this kind of quaternary alloys.

Some experiments on the growth of InTlSb by LPE

Abstract InTlSb solid solutions have been proposed as new materials to extend the IR detecting capabilities offered by III–V compounds and there have been several reports about their predicted properties and of its growth by MBE and OMCVD. In this work two types of experiments were done. First, the results of attempts to obtain the binary compound TlSb from liquids with a stoichiometric composition are reported. Second, the determination of some liquidus points of the ternary solution and the results of attempts of growing the ternary alloy In 1− x Tl x Sb by LPE on InSb substrates are also reported. Reflectance, X-ray diffraction and EDX measurements show that the epitaxial layers are InSb. Tl incorporation into the solid could not be detected by these techniques.