Distribution of nitrogen in GaInNAs/GaAs quantum wells

Quantitative high-resolution transmission electron microscopy was applied to determine the indium and nitrogen distributions in a GaInNAs/GaAs heterostructure. Two almost identical samples grown by gas-source molecular beam epitaxy on GaAs [001] substrates were investigated. The samples contained InGaAs and GaInNAs wells with the same thickness and In concentration. According to high-resolution X-ray diffractometry the average In concentration is 27% in both samples, with an N concentration of 1.1% in the GaInNAs quantum well. The evaluation of the photoluminescence peak position of the InGaAs sample and additional photoreflectance measurements yielded an In concentration of 30%. In-concentration profiles were obtained with the composition evaluation by the lattice fringe analysis (CELFA) technique for the InGaAs well using the chemical sensitivity of the [002] reflection. The averaged In concentration in the InGaAs quantum well was determined to be (30±1)% in good agreement with the other measurement techniques. The N-concentration profiles in the GaInNAs wells were measured by the comparison of the CELFA results in the samples with and without nitrogen. The N distribution is characterised by two maxima close to the GaInNAs/GaAs interfaces. The measured N concentration in the central part of the quantum well is (2.5±1.0)%.