Effect of the property of dielectric capping layers on impurity-free vacancy diffusion in InGaAs/InGaAsP MQW structures

A dependence of the interdiffusion in InGaAs/InGaAsP multiple quantum well (MQW) structures on the stoichiometry of SiO_x and SiN_x capping layers, which were deposited with different SiH₄ flow rates by plasma enhanced chemical vapor deposition (PECVD), has been studied. Decreasing the SiH₄ flow rate during PECVD deposition produces relatively more voids inside SiO_x or SiN_x film. For both SiO_x and SiN_x capping layers, the blue shift of intermixed samples after rapid thermal annealing (RTA) becomes larger due to the enhancement of the interdiffusion of well/barrier caused by the increased porosity of dielectric capping layers as SiH₄ flow rate decreases from 300 sccm to 20 sccm. Using SiO_x (SiN_x) deposited with different SiH₄ flow rates, the magnitude of blue shift is varied by about 98 nm (75 nm) for the samples annealed at 850 °C for 30 s. The blue shifts of 138 nm and 98 nm of photoluminescence peak wavelength for the SiO _x (deposited with 20 sccm SiH₄) capped MQWs without and with an InGaAs cap layer, respectively, are observed after RTA of 850 °C for 30 s. A possible mechanism is discussed for these phenomena.