Abstract

Polished (111) surfaces of monocrystalline cubic gallium arsenide GaAs platelets and a powdered microcrystalline form of GaAs were nitrided towards gallium nitride GaN under a flow of ammonia at temperatures in the range 600-900 ºC for one to several tens of hours. The progress of nitridation was followed mainly by grazing incidence X-ray diffraction GIXD and powder X-ray diffraction XRD. Morphology changes were examined with scanning electron microscopy supplemented with energy dispersive analysis SEM/EDX. Thermogravimetric and differential thermal analyses TGA/DTA were used to evaluate a thermal stability of the GaAs substrate. The substrate/temperature/time related interplay in the formation of the cubic and hexagonal GaN polytypes from cubic GaAs and conditions favoring the metastable cubic GaN polytype are delineated.

Keywords: Chemical synthesis, nitrides, crystal symmetry, nanostructures.