Characterisation of layered nanostructures requires the use of sensitive and precise techniques in depth profile analysis. Recently sputtering with ultra-low energy (below 1 keV) ion beams is used in order to reduce ion beam mixing effects [1, 2]. Here we show the results of 880 eV argon ion beam sputtering applied in secondary ion mass spectrometry (SIMS) of metal organic vapour phase epitaxy (MOVPE) grown structures.
The analysed layered systems were different quantum wells (InAlGaAs and GaAs) and barriers (AlGaAs and InAlGaAs). Typical obtained structure consisted of GaAs substrate, 150 ÷ 500 nm GaAs buffer, multi quantum well (MQW) region and 50 ÷ 70 nm GaAs cap layer. The MQW is a 3-layer period superlattice made of 9 nm thick InxAlyGa1-x-yAs layer and 30 nm thick GaAs or AlzGa1-zAs layer. The structures were obtained by AP MOVPE technology using AIX200 R&D Aixtron reactor. The growth temperature (Tg) was in the range of 650 ÷ 690C, the H2 flow rate through TMIn bubbler (VH2/TMIn) was varied from 35 to 75 sccm/min. The other growth parameters were the same as for the InGaAs/GaAs MQW structures described in [3, 4].
SIMS analyses were performed on SAJW-05 analyser equipped with 06-350E Physical Electronics ion gun and QMA-410 Balzers 16 mm quadrupole spectrometer. The results show high depth profile resolution of MQW structures with measured 12 nm FWHM of InxAlyGa1-x-yAs layers. Ion erosion of reference samples with thick (~ 500 nm) ternary alloy layers allowed for careful calibration of sputtering rates in the layers of the analysed MQW structures and also for quantitative description of stoicheiometry coefficients in these layers.
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