TEM Studies on the Microstructure of m-Face Grown 4H-SiC by Solution Growth

We have studied the microstructure of the growth surface of the 4H-SiC grown by the m-face solution growth. Atomic Force Microscopy (AFM) revealed the micro-striped morphology with the asperity of several nm in the band-like morphology region. The cross-sectional Transmission Electron Microscopy (XTEM) showed that the growth surface consisted of a bunch of nanofacets and vicinal surface. This peculiar morphology is totally different from that of conventional spiral growth on c-face, which can be closely related with the growth mechanism of the m-face solution growth.

Surface Roughness Changes Induced by Stoichiometric Deviation in Ambient Phase for Two-Component Semiconductor Crystals

The effects of a deviation in the fraction of the components in the ambient phase of a stoichiometric AB compound, such as GaN or SiC crystals, on the surface roughness and step self-assembly and disassembly on a vicinal surface are studied using the Monte Carlo method based on a staggered restricted solid-on-solid (st-RSOS) model at equilibrium. The (001) and (111) surfaces are typical examples of non-polar and polar surfaces, respectively. Although a stoichiometric deviation of the ambient phase does not affect the surface energy of a non-polar surface, it affects that of polar surfaces such as the ( 111 ) A and ( 111 ) B surfaces. We found that the vicinal surface of an AB compound is atomically smooth and globally rough. Globally, the vicinal surface is not affected by a stoichiometric deviation in the ambient phase. In contrast, in a small area, the structure of the vicinal surface is affected by a stoichiometric deviation in the ambient phase. The vicinal surface consists of local double and quadruple steps. The characteristic length L M F L , which separates the global length scale region and the local length scale region, has a maximum value of 156 a in the present study, where a is the lattice constant. When temperature decreases, L M F L can become large.

An Influence of the Si(111)3-4o Vicinal Surface on the Solid Phase Epitaxy of α-FeSi2 Nanorods and their Crystal Parameters

The morphology and structure of iron silicide nanorods formed on Si (111) vicinal surface by the SPE method at T = 630 °C were studied. Optimal Fe coverage and Fe deposition rate for the formation of a dense array of the nanorods (54-65% of the substrate area) on Si (111) surface with 3-4o miscut angles were established. The aspect ratio of the nanorods is 1.9 – 3.3. Cross-sectional images of a high-resolution transmission electron microscopy (HRTEM) have shown that the nanorods have α-FeSi2 crystal structure. They are strained along the “a” axis and stretched along the “c” axis, which increased the unit cell volume by 10.3%. According to HRTEM image analysis, the nanorods have the following epitaxial relationships: α-FeSi2[01]//Si [10] and α-FeSi2(112)//Si (111). All the data obtained have provided, for the first time, a direct evidence of α-FeSi2 nanorods formation on Si (111) vicinal surface without noticeable penetration of Fe atoms into the Si substrate.

Comparative Characteristics of GaAs and InAs Langmuir Evaporation - Monte Carlo Simulation

The process of GaAs and InAs substrates high-temperature annealing under the Langmuir evaporation conditions is studied by Monte Carlo simulation. The temperature range of gallium arsenide and indium arsenide congruent and incongruent evaporation are determined. It was demonstrated that the congruent evaporation temperature Tc is sensitive to the vicinal surface terrace width. The decrease of the terrace width results in a decrease in the congruent evaporation temperature. The Ga and In diffusion lengths along the (111)A and (111)B surfaces at congruent temperatures are estimated. The surface morphology transformation kinetic during high-temperature annealing is analyzed.

Surface Orientation Influence on the Langmuir Evaporation Characteristics of GaAs Substrates

The dependences of congruent evaporation temperature Tc and the desorption activation energies of GaAs components on the substrate surface orientation are analyzed using Monte Carlo simulation. On the vicinal surfaces with the (111)A orientation at temperatures exceeding Tc, the metal droplets start to grow at step edges, and, with the (111)B orientation, the droplets nucleate randomly on the terraces. The droplet concentration on the (111)B surface is higher than that on the (111)A surface. The droplet-crystal interface roughness is different for (111)A and (111)B orientations. The Tc of (111)B surfaces is lower than that of (111)A surfaces. For both surface orientations, Tc decreases when the vicinal surface terrace width is shorter than the double gallium diffusion length. The gallium and arsenic desorption activation energies dependence on the vicinal surface misorientation is demonstrated. A sharp increase in the arsenic desorption rate is observed with an increase of the (111)A surface coating with liquid gallium.