Thermodynamical analysis of abrupt interfaces of InGaP/GaAs and GaAs/InGaP heterostructures

Interfaces between arsenide and phosphide III-V semiconductors have shown to be one of the most difficult issues to be understood and definitively solved. This problem is particularly relevant with Vapour Phase Epitaxy (VPE) and Metallo-Organic Vapour Phase Epitaxy (MOVPE) techniques, since an irreproducibility in preparing abrupt interfaces between arsenide and phosphide has been evidenced. Several researchers have ascribed this problem to the volatility of arsenic and phosphorus species and since then for long time different recipes and growth procedures have been suggested in order to obtain sharp transition between the two different materials. In this work the film/substrate interface is modelled using thermodynamical calculations after the regular solution model proposed by Jordan and Ilegems: PH3 flows over GaAs surface, and as a consequence the substrate is enriched with P, with the formation of a thin layer of GaAsP and mixed As-P gaseous species. Samples of InGaP on GaAs substrate were grown by MOVPE and characterised by Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM) in order to support the theoretical findings. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)