High-resolution depth profiling of InxGa1-xAs/GaAs multiple quantum well structures by combination of secondary ion mass spectrometry and x-ray diffraction techniques

In this work we investigate multiple quantum well semiconductor structures by secondary ion mass spectrometry (SIMS) and high-resolution x-ray diffraction measurements. The combined use of these techniques turns out to be a very powerful tool for an accurate investigation of both structural and chemical characteristics of complex structures consisting of thin alternating layers. We show that the x-ray data allow us to increase the accuracy of the SIMS analyses providing internal standards, for both depth scale and concentration calibration. This procedure allows us: (i) to determine accurate quantitative SIMS concentration profiles which lead to the determination of the elemental concentration in the quantum wells, (ii) the mole fraction and layer thickness of embedded layers, and (iii) also to investigate eventual segregation and diffusion phenomena occurring at the interfaces. Our procedure is demonstrated on a set of InxGa1-xAs/GaAs multiple quantum well structures grown by metalorganic chemical vapor phase epitaxy. The experiments, performed by secondary ion mass spectrometry and high-resolution x-ray diffraction measurements, as well as the methodology of the data analyses are discussed in detail. As the main result of our investigation we obtained the precise indium distribution in each of the investigated samples with an accuracy below 5% and the individual barrier and well layer thickness.