Sputtering behavior and evolution of depth resolution upon low energy ion irradiation of GaAs

Abstract

The authors have investigated the sputtering behavior and evolution of depth resolution upon low energy ion irradiation during secondary ion mass spectrometry (SIMS) depth profiling of GaAs. They presented a systematic and quantitative study of the impact of ion species, primary ion impact energy, and incident angle on (evolution of) depth resolution using a well-characterized dedicated InGaAs/GaAs multilayer structure with nearly atomically abrupt heterointerfaces. They demonstrated that for low energy O2+ ion beam irradiation, the SIMS depth resolution is severely degraded by (transient) incorporation of high surface O-concentration into the altered layer, leading to detrimental ion beam induced formation of topography. They provided evidence that topography formation is primarily invoked by the strong angular dependence of the sputter yield on (local) incident angle. In the case of low energy, oblique Cs+ ion beam irradiation, the sputtering behavior of GaAs is well-behaved with no significant transient yield changes and a constant depth resolution. This enables SIMS depth profiling of sharp heteroepitaxial III–V multilayer structures and shallow dopant profiles with sufficiently good depth resolution and good detection efficiency.

High‐resolution secondary ion mass spectrometry depth profiling of nanolayers

“…Here, both λ up and λ d are ~5 nm for 24 Mg, ~2 nm for 64 Zn, and λ up = 0.4 nm for 28 Si. The measured leading and decay lengths were of the same order or better than published to‐date corresponding data obtained with commercial state‐of‐the‐art SIMS instrumentation using cluster/molecular or low energy O 2 + /Cs + ion sources, or with laser‐assisted atom probe tomography …”

“…The measured leading and decay lengths were of the same order or better than published to-date corresponding data obtained with commercial state-of-the-art SIMS instrumentation using cluster/molecular or low energy O 2 + /Cs + ion sources, or with laser-assisted atom probe tomography. [9,10,12,13,17,38,39] As mentioned above, the first 24 Mg peak of the stack was not resolved from the surface constituent, which caps the structure. In order to resolve in the depth profile the 24 Mg peak corresponding to the topmost ALD layer from the surface contamination, we decreased the duration of the individual ion milling cycles and proportionally increased their number.…”

Chemical depth profiling and 3D reconstruction of III–V heterostructures selectively grown on non‐planar Si substrates by MOCVD

“…Decreasing the energy of the oxygen primary beam below 500 eV at certain angles may lead to higher roughness and degradation of depth resolution in III–V materials. The angular and energy dependence under oxygen bombardment has already been reported elsewhere .…”