Study of the mechanisms of GaN film growth on GaAs surfaces by thermal and plasma nitridation

Abstract

The kinetics of GaAs nitridation using N 2 plasmas, both radio frequency and electron cyclotron resonance sources, is investigated using in situ and real time ellipsometry. A comparison of plasma nitridation with the more conventional NH 3 thermal nitridation of GaAs is also reported. We report that all the GaAs nitridation processes are self-limiting yielding only very thin GaN layers. The dependence of GaN layer thickness on surface pretreatment, surface temperature and N atom density in the plasma is reported. Smooth and stoichiometric GaN layers are formed at TϽ600°C, whereas nitridation at Tу600°C yields rough and Ga-rich GaN layers. In both cases, it is shown that As segregates at the GaAs/GaN interface, indicating that GaAs plasma nitridation kinetics is limited by outdiffusion of As and/or AsN species.

Gallium nitride films synthesized by reactive pulsed laser deposition from a GaAs target

“…The minor components with higher energies result from gallium bound to oxygen at the film surface. The peak shifts between the Ga-N and Ga-O bonds in both the Ga 2p and Ga 3d binding energies are consistent with those previously reported [10,11]. Figure 3 displays the XPS spectrum related to the N is core level.…”

“…From Gaussian deconvolution, three peaks can be resolved from the N is spectrum. The major component centered at 397.2 eV corresponds to nitrogen bound to gallium [10,12], whereas the component with binding energy of 399.4 eV could be assigned to N-N bonds due to the excess of nitrogen in the films. The smaller component with lower binding energy has not been precisely assigned, since we are not certain at present whether it results from the contamination due to air exposure.…”

Nucleation and growth mode of the molecular beam epitaxy of GaN on 4H–SiC exploiting real time spectroscopic ellipsometry

“…This indicates that nitridation does not occur if residual oxygen is left on the surface, and, hence, that nitrogen atoms are not able to exchange for oxygen as already demonstrated for nitridation of other substrates with residual oxygen, such as GaAs [12]. We found that 10 min of exposure to the N 2 plasma operated at 500 W and 0.7 sccm N 2 yields an increase in h 2 i of 0.06, while an increase of only 0.03 was observed when the plasma was operated at 240 W and 0.35 sccm, indicating that the extent of nitridation, and of some consequent surface roughening, depends on the atomic nitrogen density.…”

“…The SE trajectories and spectra are also consistent with the XRD and AFM measurements, which showed higher roughness and larger FWHM for XRD data of the samples whose nucleation was not optimized. XRD data indicate a FWHM of 25 arcsec and 1062 arcsec for the symmetric (0 0 0 2) and asymmetric (10)(11)(12) reflections, respectively, of the GaN grown layer-by-layer on the 200 C nitrided 4H-SiC. In contrast, XRD of GaN film grown on the unintentional nitrided SiC was degraded to a FWHM of 457 arcsec and FWHM of 1228 arcsec for (0 0 0 2) and (10-12) deflections, respectively.…”

Advanced nanoscale material processing with focused ion beams

“…An ion dose of 2.5ϫ 10 16 ions/ cm 2 has been found to be the threshold dose for the development of dropletlike precipitations at the GaAs surface. 8,9 We assume that the top surface layer is highly destabilized by the heavy ion bombardment. The diameter of the dots on the surface varies between 120 and 640 nm and the density of the dots is in the range of 1.7ϫ 10 7 dots/ cm 2 .…”