High quality thick InGaN nanostructures grown by nanoselective area growth for new generation photovoltaic devices

International audienc

Novel BGaN Nanorods and Selectivity Studies on Patterned GaN and AlN/Si (111) Tem- plates by Metal Organic Chemical Vapor Deposition

International audienc

Study of cubic GaN clusters in hexagonal GaN layers and their dependence with the growth temperature

International audienceThe inclusion of cubic phase in MOVPE-grown hexagonal GaN on GaAs substrate and its dependence with the growth temperature are investigated by high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and cathodoluminescence (CL). It is observed that the GaN layers surface exhibits 3D-grains structure. The density and shape of these grains are largely dependent on the growth temperature. HR-XRD study reveals the presence of cubic GaN clusters in the hexagonal GaN layer. Using CL we show that the cubic inclusions are not localized at the substrate/epilayer interface but propagate throughout the film

Vers l’amélioration des rendements de conversion dans la filiere des cellules InGaN/GaN

National audienc

Observation of the early stages of GaN thermal decomposition at 1200 °C under N₂

International audienceWe investigated the partial decomposition of GaN layers grown in an atmospheric pressure metal organic vapor phase epitaxy (AP-MOVPE) vertical reactor at 1200 °C under N2 ambient. In these conditions, the early stages of GaN thermal decomposition were studied. The GaN decomposition was monitored by in-situ laser reflectometry (LR). The properties of the as grown and decomposed GaN samples were analyzed by scanning electron microscope (SEM). We show that GaN decomposition starts by the formation of GaN nano-grains at the early stages. Then, due to the anisotropy of the decomposition, the GaN nano-grains are more easily etched than the GaN (0 0 .2) surface. The lateral etching may results in local smooth GaN surface formation. After that the depth etching starts again on the etched pits. Room temperature cathodoluminescence (CL) study revealed better optical properties of the GaN grains when compared to the whole GaN surface

Role of the TMG flow rate on the GaN layer properties grown by MOVPE on (hkl) GaAs substrates

International audienceThe role of the TMG flow rate on the properties of the GaN layer grown by MOVPE on (001) and (11n)/n=2,3 GaAs substrates were investigated. The surface morphology, crystalline quality and optical property were found to be strongly dependent on the TMG flow rate. As the latter decreased to 16 μmol/min, in-situ reflectance measurements showed a constant signal. This is attributed to the enhanced coalescence process, which resulted in the improvement of the surface morphology. A high TMG flow rate of 40 μmol/min sccm promoted predominantly vertical growth and resulted in the formation of a three-dimensional island. The lowest YL intensity and FWHM values of near band edge emission were obtained for GaN layers grown on (001) GaAs substrate with a TMG flow rate of 16 μmol/min, indicating an improvement of the optical properties of the GaN layer. This improvement is attributed to the coalescence process at the initial growth stage of GaN and the lateral growth process. All these behaviors were always observable whatever the used substrates. Depth resolved-CL showed that a mechanism of phase transformation in response to changing the substrate orientations

Optical Characterization Of Thick InGaN Layers For Solar Cell Applications

International audienc