We report on comparative studies of basic properties of indium nitride quantum dots (QDs) grown by metal organic vapour phase epitaxy (MOVPE) on GaN, AlN and Si(111). Variation of the growth parameters, such as the growth temperature, deposition time, and the V/III ratio, allowed us to control characteristic sizes and a density of the QDs. With similar growth parameters, both mean height and aspect ratio of the dots are increased in a GaN, AlN, Si line. The InN QDs have been encapsulated by different materials that permit us to investigate their optical response with optical excitation, whose origin, either luminescent or scattered, is discussed. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

InN is a very promising material for optoelectronics, high frequency devices and terahertz applications. However, there is no convenient matched substrate and, InN is usually grown onto sapphire. Due to the large attice mismatch and the dissimilarity in atomic arrangement, the epitaxial growth of InN onto sapphire Is a challenge. The initial stages of the growth are of primary importance for the obtention of high quality InN films. Epitaxial InN layers can be improved by nitriding the substrate but the quality of InN strongly depends on the temperature and time of nitridation used. We investigated the effect of these parameters on the crystalline quality, morphology, optical and electrical properties of InN layers. Raising the temperature and the time of nitridation is not beneficial. We also studied the effect of different buffer layers (CaN, AlN). Growth on template seems to be better than on low-temperature buffer (GaN and AlN). After optimising all parameters, we obtained InN layers on lightly nitrided sapphire which correspond, up to know and in our knowledge, to the best results in MOCVD low pressure: the layer growth mode is 2D, with a root mean square roughness of 0.62nm, a reproducible mobility of 800cm(2)/Vs and an electron concentration about 9x10(18) cm(-3). (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitride semiconductors have been at the center of semiconductor research in the last decade. However Indium nitride is still poorly known, due to its growth difficulty, and its properties are still the subject of passionate debates. Still, it is clear that it is a very promising material for telecommunication optoelectronics and hyperfrequency/terahertz applications. In particular, nanostructures based on InN are extremely interesting, by combining a small bandgap, the incredible efficiency of nitride semiconductors and the tunability of quantum dots. In this paper, we present the latest advances in the growth and optical properties of InN quantum dots grown onto GaN. The optical properties of InN dots will be compared to those of InN films, and we will show that the thermal behaviour of InN dots is far superior. Using TEM and synchrotron radiation diffraction, we will analyze the strain state of the dots at the nanometer scale, along the growth axis of the dots. These results, combined with the thermodynamical analysis of the growth data, will allow us to demonstrate that the growth mechanism is not the usual Stransky-Krastanow mode, but is more related to the BCF (Burton-Cabrera-Franck) model.

The intensity of Eu-related luminescence from ion-implanted GaN with a 10 nm thick AlN cap, both grown epitaxially by metal organic chemical vapor deposition (MOCVD) is increased markedly by high-temperature annealing at 1300 degrees C. Photoluminescence (PL) and PL excitation (PLE) studies reveal a variety of Eu centers with different excitation mechanisms. High-resolution PL spectra at low temperature clearly show that emission lines ascribed to D-5(0)-F-7(2) (similar to 622 nm), D-5(0)-F-7(3) (similar to 664 nm), and D-5(0)-F-7(1) (similar to 602 nm) transitions each consist of several peaks. PL excitation spectra of the spectrally resolved components of the D-5(0)-F-7(2) multiplet contain contributions from above-bandedge absorption by the GaN host, a GaN exciton absorption at 356 nm, and a broad subedge absorption band centred at similar to 385 nm. Marked differences in the shape of the D-5(0)-F-7(2) PL multiplet are demonstrated by selective excitation via the continuum/exciton states and the below gap absorption band. The four strongest lines of the multiplet are shown to consist of two pairs due to different Eu3+ centers with different excitation mechanisms. (c) 2005 American Institute of Physics.