Formation of interfaces in InGaP/GaAs/InGaP quantum wells

Interfaces (IFs) of In0.485Ga0.515P/GaAs/In0.485Ga0.515P quantum wells (QWs ) grown by LP-MOVPE technology were studied, and a significant influence of growth conditions on properties of the QWs was observed and theoretically analysed. The paper shows that a low-band-gap ternary or quaternary interla yer (IL) between the bottom InGaP barrier and the GaAs well layer is the ge neral reason for the deterioration of the IF quality. Such an IL forms spon taneously during the growth. Its formation can be enhanced using an inappro priate growth switching sequence and temperature. An As-to-P exchange proce ss was found to be the dominant mechanism of the formation of the IL at a g rowth temperature of 560 degrees C. An In0.485Ga0.515As monolayer (ML), cre ated by the P-to-As exchange mechanism, is always present at the InGaP/GaAs IF. Even such an ML can considerably deteriorate properties of the QW. A p roper switching sequence with thin GaP ILs grown at the Ifs can eliminate t he influence of spontaneous intermixing processes. We have calculated the q uantized energy levels of QWs, which contained IL of various compositions a nd thicknesses. The results of calculation were compared with experimentall y determined energies obtained from photoluminescence (PL) measurements. Ba sed on this comparison, thicknesses of the ILs were estimated. Only small i nfluence of As interdiffusion into the barriers and a negligible influence of indium carry-over into the GaAs well material were observed. From an ana lysis of the results it follows that about 1 ML thick ILs are spontaneously formed at the growth conditions used. (C) 2000 Elsevier Science B.V. All r ights reserved.