J. C. Ferrer

Self‐assembled quantum dots of InSb grown on InP by atomic layer molecular beam epitaxy: Morphology and strain relaxation

Self‐organized InSb dots grown by atomic layer molecular beam epitaxy on InP substrates have been characterized by atomic force and transmission electron microscopy. Measurement of high‐energy electron diffraction during the growth indicates a Stransky–Krastanov growth mode beyond the onset of 1.4 InSb monolayer (ML) deposition. The dots obtained after a total deposition of 5 and 7 ML of InSb present a truncated pyramidal morphology with rectangular base oriented along the 〈110〉 directions, elongated towards the [110] direction with {111}B lateral facets, with {113}/{114}/{111}A lateral facets in [110] views, and (001) flat top surfaces. The mismatch between the dot and the substrate has been accommodated by a network of 90° misfit dislocation at the interface. A corrugation of the InP substrate surrounding the dot has been also observed.

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.

Well surface roughness and fault density effects on the Hall mobility of In[sub x]Ga[sub 1−x]As/In[sub y]Al[sub 1−y]As/InP high electron mobility transistors

In this work, we present a correlation between the morphological characterization of InyAl1−yAs/InxGa1−xAs heterostructures grown on InP substrates for high electron mobility transistors (HEMTs) applications as determined by transmission electron microscopy, and the electrical behavior of the two-dimensional electron gas (2DEG) confined in the InGaAs channel. Our main goal is to analyze the origin of the low and anisotropic values of 2DEG Hall mobilities, discussing the effect of the density and asymmetric distribution of stacking faults and the surface undulation induced by a three-dimensional (3D) growth mode, depending on the growth temperature (Tg) and thickness (tw) of the InxGa1−xAs well. Our results have shown that a high mobility for a matched channel is obtained if the In0.53Ga0.47As layer is grown at 530 °C. Lower temperatures reduce the mobility values and lead to higher mobilities for [110] due to the surface corrugation along [110] induced by lateral decomposition of the InGaAs at low growth...

Correlation of electrical anisotropies of HEMT devices with defect distribution and InGaAs well roughness

In this study we used transmission electron microscopy (TEM) to assess the origin of the electrical behaviour of two dimensional electron gas (2DEG) in high electron mobility transistors (HEMTs) based upon InAlAs/InGaAs heterostructures grown on InP substrates, as a function of the growth temperature (Tg) of the InxGa1 − xAs well. The highest mobility for a matched channel was obtained for an In0.53Ga0.47As layer grown at 530 °C. Lower temperatures reduced the mobility values and led to higher mobilities for [110] due to the surface corrugation along [110], induced by lateral decomposition of the InGaAs at low growth temperatures.

Structural analysis of thermally oxidized amorphous Si 1-x Ge x layers

Abstract The study of the oxidation process of amorphous SiGe alloys is reported from the microstructural characteristics of the obtained oxides by wet oxidation at 700 °C during 30 minutes. The analysis has been carried out by TEM, Raman, FTIR and XPS measurements which reveal that the whole layers are partially oxidized, (Si,Ge)O y , without Ge pile-up. The deduced suboxides concentrations show the preferential silicon oxidation in spite of the simultaneous oxidation of Si and Ge. Likewise, a comparison with the oxidation of the polycrystalline alloys is performed to stand out the role of the Si and Ge diffusivities.

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.

Evaluation of atomic exchange in GaAs∕GaP interfaces by tetragonal distortion measurements

The quantification of interdiffusion processes in the interfaces of GaAs quantum wells, with thickness ranging from one to six atomic layers, grown by atomic layer molecular beam epitaxy in a GaP matrix is addressed. The atomic row positions have been determined from high resolution transmission electron microscopy images. The distortion of distances and angles between neighboring rows with respect to those expected in the strained structure has been related to changes in chemical composition. This method appears more efficient for this system than other methods based on the analysis of the atomic row contrast. Results show that interdiffusion occurred at the GaAs∕GaP interfaces. The arsenic profiles in the quantum well suggest that the main contribution of interdiffusion comes from atomic exchange. The experimental profiles have been fitted to a simple model of segregation giving segregation coefficients around 0.45. The results are compared to simulations based on Raman measurements performed on the sam...

Silicon Recrystallization in Sipos Material Obtained by Disilane

Conventional and Rapid Thermal Annealing of Semi-Insulating Polycrystalline Silicon layers obtained by Low Pressure Chemical Vapor Deposition (LPCVD) from disilane Si 2 H 6 have been performed in order to determine the structural modifications induced on the layers by these thermal treatments. The study of these modifications has been carried out by several analysis methods like FTIR, XPS, TEM, RAMAN and ellipsometry. The results obtained are presented, contrasted and discussed in this work.