MOVPE of AlGaAsSb using TTBAl as an alternative aluminum precursor

We investigated the metal organic vapor pressure epitaxy growth of AlxGa1-x AsySb1-y on InAs substrates using the precursors tritertiarybutylaluminum ( TTBAl), triethylgallium (TEGa), tertiarybutylarsine (TBAs) and triethylanti mony (TESb). Optimization of the substrate stabilization, the annealing tim e and the purging time between stabilization and growth was necessary to ac hieve reproducible solid composition, high structural quality and mirror-li ke surface morphology. To avoid phase separation in the material, substrate temperatures higher than approximately 610 degreesC were required. The bes t electrical properties were achieved for V/III-ratios between 1.8 and 4 wi th growth temperatures between 625 degreesC and 645 degreesC. With increasi ng x(A1) from 0.20 to approximately 0.48, the p-type background doping leve l increased from 4x10(17)cm(-3) up to 2x10(18)cm(-3) whereas the correspond ing mobilities decreased from 150 to 50cm(2)/V s. SIMS measurements indicat e that the increased hole concentration is due to carbon incorporation. Usi ng new "EpiPure" TEGa and TESb batches supplied by Epichem Ltd.. which were synthesized using a completely oxygen-free route, the electrical and optic al properties of AlGaAsSb were improved. (C) 2000 Elsevier Science B.V. All rights reserved.