Search

We have studied the growth of GaN layers by the metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates at various reactor pressures, including ones above the atmospheric level. It is established that the epitaxial growth at higher pressures does not affect the crystalline perfection of epilayers, their electron mobility, and background impurity level, but leads to the formation of GaN surface with lower lateral scale of inhomogeneities. In addition, the reactor pressure influences the ratio of edge and impurity lines in the photoluminescence spectra and leakage current level in reversely biased Schottky barriers. [ABSTRACT FROM AUTHOR]

A combined experimental and modeling study of stress and curvature evolution during (0001) GaN growth on (0001) 4H-SiC wafers is presented. It is shown that the GaN layers are under the compressive stress, whose magnitude depends on the composition of the AlGaN buffer that is used to accommodate the epitaxial strain between GaN and SiC. Processing of in situ curvature measurements suggests fast relaxation of the mismatch stress in GaN when the Al content is increased. At that, nucleation of new dislocations is possible, but the dislocation density decreases rapidly over a narrow part of the GaN layer due to large inclination and annihilation of the threading dislocations. Eventually, correlations between the curvature/stress/dislocation evolution and AlGaN buffer composition can be established and optimal strategy for the growth of crack-free structures can be suggested. [ABSTRACT FROM AUTHOR]

Structural and optical properties of InAlN/GaN distributed Bragg reflectors grown by MOCVD on sapphire substrates are studied. The influence of growth conditions and thicknesses of the InAlN layers on structural properties of distributed Bragg reflectors is studied. It is shown that optimization of the conditions of epitaxial growth makes it possible to design InAlN/GaN distributed Bragg reflectors with a reflectance of more than 99% and a reflection maximum in the wavelength range of 460–610 nm. [ABSTRACT FROM AUTHOR]

Optical and light-emitting diode structures with an active InGaN region containing short-period InGaN/GaN superlattices are studied. It is shown that short-period superlattices are thin two-dimensional layers with a relatively low In content that contain inclusions with a high In content 1–3 nm thick. Inclusions manifest themselves from the point of view of optical properties as a nonuniform array of quantum dots involved in a residual quantum well. The use of short-period superlattices in light-emitting diode structures allows one to decrease the concentration of nonradiative centers, as well as to increase the injection of carriers in the active region due to an increase in the effective height of the AlGaN barrier, which in general leads to an increase in the quantum efficiency of light-emitting diodes. [ABSTRACT FROM AUTHOR]

We have studied the pyrolysis of trimethylaluminum (TMA) in a nitrogen-containing atmosphere of a vapor phase epitaxy reactor. It is established that, in the presence of gallium nitride coatings in the reactor, the main product of TMA pyrolysis in a nitrogen-hydrogen atmosphere is aluminum nitride. Using this process (without introducing ammonia), we obtained perfect epitaxial aluminum nitride layers. [ABSTRACT FROM AUTHOR]

The influence of hydrogen and nitrogen as carrier gases on the rates of gallium nitride (GaN) growth and etching in the process of metalorganic vapor phase epitaxy (MOVPE) have been studied. Based on these data, the possible roles of hydrogen and nitrogen in the events on the surface of an epitaxial GaN layer are considered. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]