Impurity-free interdiffusion in GaAs/Al/sub 0.54/Ga/sub 0.46/As multiple quantum wells capped with PECVD SiO/sub x/: effect of nitrous oxide flow

Abstract

Impurity-free vacancy interdiffusion of GaAs/Al/sub 0.54/Ga/sub 0.46/As quantum wells (QWs) was achieved using SiO/sub x/ capping followed by rapid thermal annealing at 950/spl deg/C. The SiO/sub x/ films were plasma deposited using N/sub 2/O/SiH/sub 4/ flow at 300/spl deg/C and 20 W rf power. The stoichiometry of capping layers were altered by varying the flowrate of N/sub 2/O. In the samples studied, the above process allows continuously variable energy shifts as high as /spl sim/15O meV while still maintaining clearly resolved excitonic behavior. The degree of intermixing is not controlled by x only but, also, by the density of the SiO/sub x/ layers, Our results, therefore, suggest that, in addition to the solid solubility of Ga in SiO/sub x/, intermixing in SiO/sub x/ capped MQW heterostructures depends on the mobility of Ga atoms in the oxide caps.