A. Barski

INFLUENCE OF THE SURFACE MORPHOLOGY ON THE YELLOW AND EDGE EMISSIONS IN WURTZITE GAN

In this letter we examine an influence of surface morphology on yellow and edge emissions in wurtzite phase GaN. Our cathodoluminescence measurements show that the yellow emission does not correlate with the surface morphology, but simultaneously the “edge” emission shows very strong spatial fluctuations. The observed effect is attributed to granular structures in GaN films and enhancement of the yellow emission in the interface region.

Time‐resolved photoluminescence studies of GaN epilayers grown by gas source molecular beam epitaxy on an AlN buffer layer on (111) Si

Optical properties of GaN epilayers grown by gas source molecular beam epitaxy on a (111) Si substrate with an AlN buffer layer are described. The mechanism of energy transfer between different excitonic emissions is proposed based on the results of time‐resolved photoluminescence (PL) and PL kinetics measurements. It is suggested that tunneling of excitons between bound and free excitons is responsible for the observed PL decay transients and their temperature dependence.

Cathodoluminescence depth-profiling studies of GaN/AlGaN quantum-well structures

In this paper we evaluate the in-depth homogeneity of GaN epilayers and the influence of electric field present in strained GaN/AlGaN heterostructures and quantum wells on the yellow and “edge” emission in GaN and AlGaN. Our depth-profiling cathodoluminescence measurements show an increased accumulation of defects at the interface. Inhomogeneities in the doping level are reflected by the enhancement of the yellow emission in the interface region. The piezoelectric effect is found to strongly reduce the emission from the strained AlGaN quantum-well barriers. We also show that Ga droplets, commonly found on surfaces of samples grown in Ga-rich conditions, screen the internal electric field in a structure and thus result in a local enhancement of the edge emission intensity.

Epitaxial growth of cubic GaN and AlN on Si(001)

Thermal treatment under propane at 1300-1400 °C has been used to prepare Silicon (001) wafers for subsequent growth of cubic GaN and AlN by Electron Cyclotron Resonance Plasma Assisted Molecular Beam Epitaxy (ECRMBE). Thermal treatment of Silicon wafers under propane, used in this experiment, produced a very thin (40 A) layer of cubic SiC on the Silicon (001) surface. Despite an extremely low thickness of as-produced SiC layer, high quality cubic GaN has been successfully grown. The cubic form of AlN grown on the SiC(40A)/Si(001) surface has also been observed despite a very high density of stacking faults.

Surface morphology of cubic and wurtzite GaN films

Abstract We describe a comparative study of surfaces of gallium nitride films grown by a variety of techniques at low growth temperatures (molecular beam epitaxy and laser-assisted chemical vapour deposition) as well as by metalorganic chemical vapour deposition. The cubic, wurtzite and mixed phase cubic–wurtzite films were grown on buffers, these included ultrathin (4 nm) SiC as well as more commonly used AlN. We find that the surface morphology of GaN films grown by MBE shows micrometer-scale structures which reflect the symmetry of the film. Surface topography may thus be used as an identification measure of film symmetry. Monochromatic cathodoluminescence images taken at the maximum of the band edge emission show granular structures reflecting surface morphologies, whereas similar structures are only very weakly visible in the red/yellow band.

Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum well structures

We studied high quality quasihomoepitaxial AlGaN/GaN quantum well (QW) heterostructures with high internal electric fields which lead to significant red shifts of exciton emission in wider QWs and an unusually long decay kinetics. The strong electric fields in the structures cause a significant change in the electron penetration range. The fields can be screened under intense electron beam excitation. We propose that electric field fluctuations are the reason for the observed in-plane variation of the CL intensity.