Growth Mechanism Of GaAs Research Articles

Growth mechanism of GaAs on (110) GaAs studied by high-energy electron diffraction and atomic force microscopy

Using in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM) we have studied the homoepitaxial growth on the (110) surface of GaAs. RHEED intensity oscillations indicate a layer-by-layer growth mode. The RHEED intensity oscillation frequency, however, decreases at a constant Ga flux with increasing substrate temperature and decreasing As flux, resulting in a lower apparent growth rate. AFM images of the surfaces reveal that at low As pressures large triangular shaped islands that ultimately lead to a rough surface are formed. The size and height of the islands increase and their density decreases with decreasing As pressures. In the area between the islands up to 1 μm large islands and terraces of monolayer height are found. The AFM images indicate that growth via step-propagation on the islands and the monolayer stepped areas between the islands, not contributing to RHEED intensity oscillations, can account for the decrease in the apparent growth rate. For very low growth rates surface roughening due to island formation during growth is completely suppressed, resulting in a well ordered terraced surface with monolayer high steps and up to 0.5 μm large terraces that are due only to the unintentional 0.04° misorientation of the substrates. The formation of these large terrace sizes is due to the surprisingly large diffusion length of the Ga on the (110) surface.

Growth mechanism of GaAs by metalorganic vapor phase epitaxy

We observed concentric ring patterns on metalorganic vapor phase epitaxy grown GaAs surface by atomic force microscopy. The growth mechanism for the concentric ring pattern is different from that of spiral growth due to screw dislocations. A more plausible growth mechanism for the concentric rings is the stacking fault mechanism. Stacking faults that emerge from the (100) growth surface create steps of 1/3 and 2/3 the elementary height. The 1/3 and 2/3 substeps act as persistent step sources for growth.

Realization of low facet density and the growth mechanism of GaAs on GaAs(110) by migration-enhanced epitaxy

Smooth GaAs layers were successfully grown by migration-enhanced epitaxy on exactly (110) oriented substrates. The surface of layers grown by conventional molecular beam epitaxy was completely covered with facets, whose density was higher than 106 cm−2. The facet density was reduced remarkably by three orders of magnitude using the migration-enhanced epitaxy method. Observing the intensity oscillations of the specular spot of reflection high-energy electron diffraction patterns, the growth mode and the migration characteristics of surface adatoms have been investigated.

Growth process of III–V compound semiconductors by migration-enhanced epitaxy

The growth mechanism of GaAs and AlGaAs in migration-enhanced epitaxy is investigated by RHEED observation and optical scattering measurements. The available Ga site density on a (2 × 4) reconstructed GaAs (001) surface is much less than the ideal density due to a missing As-dimer array structure. The layer-by-layer growth of GaAs by migration-enhanced epitaxy proceeds by repeated formation and annihilation of small Ga droplets. The growth process is also investigated by studying growth on singular and vicinal (001) GaAs planes. The observed step-flow growth is explained by considering the different chemical characteristics of the steps along the [110] and [ 1 10] directions. The results are compared with those of other growth methods such as molecular beam epitaxy and metalorganic vapor phase epitaxy.

Growth Mechanism of GaAs and AIGaAs by Migration-Enhanced Epitaxy

Growth Mechanism of GaAs and AIGaAs by Migration-Enhanced Epitaxy

Growth Mechanism of GaAs during Migration-Enhanced Epitaxy at Low Growth Temperatures

The growth process of GaAs during migration-enhanced epitaxy at low temperatures is investigated using reflection high-energy electron diffraction. Observation of specular beam intensity during growth reveals that a flat growing surface is maintained at 300°C even when the number of Ga atoms deposited per cycle is not equal to the surface site number. The composition at the growing surface can deviate considerably from stoichiometry at low temperatures because of excess As adsorpt ion. This problem is avoided by optimizing the number of As4 molecules deposited per cycle. The optimum number of As4 molecules was discussed with respect to the number of Ga atoms on the growing surface.

Effects of hydrogen on growth mechanism of GaAs in chemical beam epitaxy

We found that introduction of hydrogen gas during GaAs epitaxial growth into a chemical beam epitaxy (CBE) system decreases the growth rate and reduces the incorporation of donor impurities. We propose a simple model that hydrogen gas adsorbs on the GaAs substrate and the adsorbed hydrogen prevents the metalorganic gas and some other impurity gases from adsorbing on the surface to explain these results.