T. Utzmeier

Raman scattering of InSb quantum dots grown on InP substrates

In this paper we present the Raman scattering of self-assembled InSb dots grown on (001) oriented InP substrates. The samples were grown by pulsed molecular beam epitaxy mode. Two types of samples have been investigated. In one type the InSb dots were capped with 200 monolayers of InP; in the other type no capping was deposited after the InSb dot formation. We observe two peaks in the Raman spectra of the uncapped dot, while only one peak is observed in the Raman spectra of the capped dots. In the case of the uncapped dots the peaks are attributed to LO-like and TO-like vibration of completely relaxed InSb dots, in agreement with high resolution transmission electron microscopy photographs. The Raman spectra of the capped dot suggest a different strain state in the dot due to the capping layer.

Growth and characterization of self-organized InSb quantum dots and quantum dashes

We have grown self-organized InSb quantum dots on semi-insulating InP (0 0 1) substrates by molecular beam epitaxy. The size dependency of the uncapped InSb quantum dots on the nominal thickness of the deposited InSb was studied by atomic force microscopy. The dot size has a pronounced minimum at about 2.2 monolayers of InSb. After a nominal thickness of 3.2 monolayers we observe a drastic change of the dot shape, from quantum dots to quantum dashes. From thereon the dots grow in a quasi-cylindric shape aligned in the (1 1 0) direction. The photoluminescence emission of a series of quantum dots was studied, the emission energy being independent of the dot size. When the dots partially relax, the photoluminescence is blue-shifted, which can be explained by a type-II band alignment.

A new in situ III-V surface characterization technique: chemical modulation spectroscopy

Abstract A new in situ technique for the study of the molecular beam epitaxy (MBE) growth process of III–V compounds based on the chemical modulation of the surface has been developed. In this technique, the anisotropic optical reflectivity is modulated by a periodic variation of the surface stoichiometry induced by using group V pulsed molecular beams. Pulses are produced by valved pulsed cells for group V elements (As, P, Sb) that we use for atomic layer molecular beam epitaxy (ALMBE) growth. The substrate is maintained at sufficiently high temperature in order to obtain rapid desorption of group V molecules from surface during flux interruptions, and the process is monitorized by reflection high energy electron diffraction (RHEED). Linearly polarized light, reflected at near normal incidence by the sample, is collected independently along one of the two principal axes of the crystal, [1 1 0] and [1 1 0]. This technique has been applied to the surfaces of epitaxial (1 0 0) layers of GaP, GaAs, GaSb, InP, InAs, and InSb grown by MBE. Spectra in the 1–3 eV range show well defined peaks for light polarized along [1 1 0] and [1 1 0] directions, parallel to group III and group V dimers, at specific energies for each compound.

RESONANT RAMAN SCATTERING STUDY OF INSB ETCHED BY REACTIVE ION BEAM ETCHING

A Raman study of InSb etched by reactive ion beam etching using a CH4/H2/N2 plasma generated by electron cyclotron resonance is presented. The evolution of the LO, 2LO phonon and phonon–plasmon coupled modes has been studied using resonant Raman spectra in different configurations. Results indicate an increase of the carrier density by a factor of about 60 and a decrease of the built‐in potential due to the plasma process. The combination of both evolutions results in a prevalence of the electric field induced scattering upon the defect induced scattering mechanism.

Growth and characterization of InSbInP short-period strained-layer superlattices grown by almbe

We report for the first time the successful growth of short period strained-layer superlattices of InSbInP by atomic layer molecular beam epitaxy. This sample combination is especially interesting because the equivalent ternary alloy has a very wide miscibility gap in which it cannot be grown. The samples were characterized by reflection high-energy electron diffraction, X-ray diffraction, Hall measurements and Raman spectroscopy. The X-ray measurements show clearly satellite peaks that indicate the formation of the superlattice. Raman spectra show the confined phonon peaks of InSb (194 cm−1) and InP (300 cm−1), respectively. Exciting in resonance with the E1 transition of the SPSL the peaks corresponding to the LO1 and LO2 phonons are clearly identified.

Morphology evolution of InSb island grown on InP substrates by atomic layer molecular beam epitaxy

Abstract The growth evolution of capped InSb quantum dots grown on InP(001) substrates is reported for a range between 0.6 and 15 monolayers of InSb deposited by atomic layer molecular beam epitaxy. TEM studies have been performed in order to follow the progression in dot size and morphology. After the transition from an initial two-dimensional to a three-dimensional growth mode at 1.1 ML there is a range in which InSb nanometre scale islands are homogeneously distributed. Raman spectra have also been recorded to assess the effects of the introduction of the capping layer covering the islands, comparing the results with those of uncapped samples. The activation of the InSb TO mode is discussed in terms of the facetting of the dots by (001) and {111} sides observed prior to the cap deposition.