Z. Benzarti

Study of GaAs layers grown on Ge substrates by MOVPE and in situ monitored by laser reflectometry

Metalorganic vapor phase epitaxy (MOVPE) of GaAs on Ge substrate has been studied by laser reflectometry (LR) with 632.8 nm laser beam. The layers were grown by varying substrate temperature and the V/III ratio. The relative difference between refractive index of film and substrate results in pronounced easily detected interference oscillations in the reflected beam intensity. The oscillations period provides an accurate and immediate measure of growth rate. In addition, the variations of extrema of oscillations and the average value of reflectance provide an estimate of the quality and surface roughness. A procedure for quantifying the roughening observed during the in situ LR monitoring of growth was presented. Furthermore, the measured interference effects were analyzed by calculating the reflectance. In order to explain the reflectometry behavior, the film was also characterized by X-ray diffraction and scanning electronic microscopy.

Effect of SiN Treatment on Optical Properties of InxGa1−xN/GaN MQW Blue LEDs

In this paper, Si-doped GaN template layer and nitride-based multiple quantum well (MQW) light-emitting diodes (LEDs) with conventional GaN buffer layer and GaN buffer layer using SiN treatment were elaborated by metalorganic vapor phase epitaxy (MOVPE). On both kinds of structures, five InxGa1−xN/GaN quantum wells were deposited simultaneously in identical growth conditions. GaN template layer defects that influence on the growth of InxGa1−xN/GaN MQW LEDs were systematically studied by means of scanning electron microscopy, high-resolution x-ray diffraction, temperature-dependant photoluminescence measurement, and electroluminescence. It is shown that optical properties of InxGa1−xN/GaN MQWs depend on the defect density of elaborated templates. Thereafter, we report an enhancement of the emission of blue MQW LEDs using SiN treatment, compared to the MQW LED emissions deposited on a conventional GaN buffer layer.