| This doctoral project proposes to study the incorporation of nitrogen to GaAs epitaxial layers grown on GaAs(001) substrates, a system that allows for systematically isolating the effect of nitrogen from that of indium. In this thesis we report on the results of a work where the focus was brought on (i) the growth kinetics of GaAs1-xNx during the metal-organic vapour phase epitaxy growth (OMVPE) (ii) the analysis of the physical and structural properties of GaAs1-xNx/GaAs heterostructures and (iii) the characterization of the nitrogen incorporation sites in the GaAs crystal lattice. Moreover, we present the results of exploratory studies aiming at the production of GaAs1-xN x/GaAs multilayers and to the growth of InyGa1-yAs1-x Nx quaternary alloys. These latter studies address issues that are closer to technological applications since they focus on process details pertaining to the fabrication of devices.; Trimethylindum (TMIn), trimethylgallium (TMGa), tertiarybutylarsine (TBAs) and dimethylhydrazine (DMHy) were used as organometallic sources, a quite original combination since not widely encountered in the epitaxial growth field. TBAs has the great advantage of being far less dangerous than arsine in OMVPE processes, the latter being highly toxic and more prone to causing leaks on a large scale. Regarding the diversity of the growth parameters, the GaAs1-xNx/GaAs samples grown for this project definitely constitute one of the largest bank of its kind. The systematic monitoring of both the growth rate and the composition of these materials under varying growth conditions has, as a consequence, generated an impressive quantity of experimental data. In addition to the DMHy flow rate, the investigated parameters include, among others, the reactor pressure, the TMGa flow rate, the substrate temperature (from 500 to 650°C), and the V/III ratio. Not only have those results allowed to highlight important behaviors of the chemical species involved in surface reactions, but they also allowed for pointing out an important lack of knowledge on the decomposition pathways of the organometallics sources.; Nitrogen incorporation in GaAs being very inefficient, exceptionally high flow rates of DMHy are required, which sometimes lead to V/III ratios greater than 500. Depending on the growth temperature, this excess of DMHy molecules on the growth surface affects the growth rate and the incorporation efficiency in a complex way. Moreover, the sensitivity of x with respect to the gas phase composition translates into a laterally non-uniform incorporation of N during the growth of epilayers with high nitrogen content. For low temperatures and extremely large flow rates of DMHy, this precursor occupies most of the adsorption sites on the growth surface, thus leading to drastic reduction of the growth rate accompanied by a very large N incorporation (x > 0,1). High resolution X-ray diffraction (HR-XRD) and heavy ion Rutherford backscattering spectroscopy (HIRBS) analyses suggest that the epilayers deposited under such conditions undergo a phase separation and exhibit an important non-stoechiometry, probably indicative of an amorphous matrix.; Our results also allowed us to identify and explain a nonlinear variation of the GaAs1-xNx lattice parameter a as a function of its composition x. (Abstract shortened by UMI.)... |
