An Optical Study of Interdiffusion in Strained InP-Based Heterostructures

The interdiffusion behavior of In1- x Ga x As1- y P y /In1- x ′ Ga x ′ As1- y ′ P y ′ multiple quantum well heterostructures with varied built-in strain and layer thicknesses, has been investigated by monitoring their photoluminescence (PL) properties. All samples annealed at 850° C, have consistently exhibited a blueshift of the heavy hole exciton line as a result of atoms interdiffusion across the heterointerfaces. A quantitative analysis of their PL spectra permitted to deduce the following important characteristics of the interdiffusion process: (i) From the data on a nearly strain-compensated structure with constant P/As ratio and In-rich wells, studied here for the first time, we show that the blueshift of the excitonic line is consequent of group III atoms interdiffusion alone, like in GaAs/GaAlAs system, and the In-Ga interdiffusion can be described with a diffusion coefficient D In-Ga≈4.72×10-16 cm2/s; (ii) In the case of lattice matched and compressively-strained structures, a simultaneous interdiffusion on group III and V sublattices has been assumed to yield an effective interdiffusion coefficient ranging from 3.83 to 5.51×10-16 cm2/s.