Function Of Ga Flux Research Articles

Structural characterisation of zinc-blende Ga 1−xMn xN epilayers grown by MBE as a function of Ga flux

Zinc-blende Ga 1− x Mn x N epilayers grown by plasma-assisted molecular beam epitaxy as a function of Ga flux are assessed using a variety of structural characterisation techniques. The Ga:N ratio was found to have a dominant impact on the zinc-blende Ga 1− x Mn x N epilayer growth rate and resultant composition, morphology and microstructure. A maximum growth rate and an improved microstructure are associated with growth under slightly Ga-rich conditions. A reduced growth rate and enhanced Mn incorporation are associated with growth under slightly N-rich conditions. α-MnAs inclusions and voids extending into the GaAs buffer layer were observed in all cases, however they are considered not to affect the layer electrical and magnetic properties.

Surface reconstruction and surface morphology of GaN grown by MBE on GaAs (001)

RF-plasma assisted molecular beam epitaxy growth was used to study surface reconstruction and surface morphology as a function of Ga-flux and the plasma excitation power for growth of GaN on GaAs (001) at 580°C. In the initial growth stage a (3 × 3) surface reconstruction was observed. This surface periodicity only lasted up to a maximum thickness of 2.5ML, which was followed by a new transition to the unreconstructed surface. We found that the smoothest surfaces were provided by the N/Ga-ratio giving the thickest layer at the (3 × 3) ⇒ (1 × 1) transition. The growth rate providing optimum growth conditions was shown to increase with the activation power of the RF-source, i.e. the amount of active nitrogen. Using this information, a series of samples were grown at maximum RF-source power in order to find the optimum N/Ga-flux ratio at highest possible growth rate. Characterisation by SEM indicted that the best surface morphology was obtained at a growth rate of approximately 0.3 µm/h.

Surface Morphology of MBE-grown GaN on GaAs(001) as Function of the N/Ga-ratio

Molecular beam epitaxy growth utilising an RF-plasma nitrogen source was used to study surface reconstruction and surface morphology of GaN on GaAs (001) at 580 °C. While both the nitrogen flow and plasma excitation power were constant, the grown layers were characterised as a function of Ga-flux. In the initial growth stage a (3×3) surface reconstruction was observed. This surface periodicity only lasted up to a maximum thickness of 2.5 ML, followed by a transition to the unreconstructed surface. Samples grown under N-rich, Ga-rich and stoichiometric conditions were characterised by high-resolution scanning electron microscopy and atomic force microscopy. We found that the smoothest surfaces were provided by the N/Ga-ratio giving the thickest layer at the (3×3)=>(1×1) transition. The defect formation at the GaN/GaAs interface also depended on the N/Ga-flux ratio.