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Be and Si migration in AlGaAs/GaAs heterostructures during molecular beam epitaxy

: Maier, M.; Gaymann, A.

Gillen, G.; Lareau, R.; Bennett, J.; Stevie, F.:
Secondary ion mass spectrometry. SIMS XI. Proceedings of the Eleventh International Conference on Secondary Ion Mass Spectrometry
Chichester: Wiley, 1998
ISBN: 0-471-97826-4
International Conference on Secondary Ion Mass Spectrometry (SIMS) <11, 1997, Orlando/Fla.>
Fraunhofer IAF ()
AlGaAs/GaAs; diffusion; MBE; secondary ion mass spectrometry; Sekundärionen-Massenspektrometrie

AlGaAs/Ga.As multi quantum well laser structures grown by molecular beam epitaxy (MBE) are usually doped with the p- and n-type dopants Be and Si, respectively. High growth temperatures are required to obtain a good device performance. In addition, high dopant concentrations are chosen to obtain a low series resistance. Therefore, dopant migration due to both diffusion and surface segregation is critical, which would result in reduced device performance. The dopant profiles can be checked by SIMS depth profiling. Due to the varying Al content in the laser structures, SIMS is complicated by the matrix effect. Both the sputtering rate and the relative sensitivity factors (RSFs) for quantitative calibration depend on the Al content. Artificial dopant spikes appear at heterointerfaces due to the abrupt change of the ionization probability. In this paper, both sputtering rates and RSFs are studied in a quadrupole type instrument as a function of the Al content and the primary beam energy us ing oxygen 02(+) and cesium Cs+ primary ions. A Be doped AlGaAs/GaAs heterostructure is analyzed, which exhibits pronounced Be spikes at the heterointerface due to solid solubility and diffusion effects. The depth profiles of Be and Si are investigated in a vertically compact AlGaAs/GaAs laser structure grown on top of a high electron mobility transistor structure needed to fabricate optoelectronic integrated circuits.