Silane flow rate dependence of SiOx cap layer induced impurity-free intermixing of GaAs/AlGaAs quantum wells

Impurity-free intermixing of GaAs/Al0.54Ga0.46As quantum wells was carried out using SiOx capping layers grown by plasma enhanced chemical vapor depos ition followed by rapid thermal annealing at 950 degrees C. A dependence of quantum well intermixing on the quality of dielectric layer was observed, which was varied by changing the silane flow rate, M (40 sccm less than or equal to M less than or equal to 480 sccm). The quality of capping layers w ere determined using Rutherford backscattering spectroscopy, spectroscopic ellipsometry, secondary ion mass spectrometry, Fourier transform infrared s pectroscopy, and P-etch measurements. The porosity and oxygen content of ca pping layers, and the incorporation of nitrogen during deposition were the main factors influencing the extent of blue shifts achieved in intermixed q uantum wells. Substantially higher energy shifts were obtained for capping layers deposited using M < 160 sccm. Slightly overstoichiometric layers whi ch were relatively more porous but containing less nitrogen were obtained f or M < 160 sccm. For higher silane flow rates, substoichiometric oxide laye rs with increased hydrogen and nitrogen contents were obtained. Our results suggested that the mobility of out-diffusing Ga atoms during annealing was enhanced by film porosity but was suppressed with increasing nitrogen cont ent in the capping layer. (C) 2000 The Electrochemical Society. S0013-4651( 99)03-100-6. All rights reserved.