A laterally selective interdiffusion enhancement of GaAs/AlGaAs quantum well using a buried Al-oxide layer is investigated with a selectively oxidized region. The defects within the interface of Al-oxide layer make 3-group elements interdiffusion be enhanced. To examine the effect of QW interdiffusion enhancement, the samples were patterned into 200㎛ wide stripe mesas and oxidized 50 ㎛ with each side. Annealing temperature was 950℃ ± 5℃. And to measure the QW energy shift, Photoluminescence peak wavelength shifts were detected. PL peak shifts of QW under Al-oxide layer region is twice as much as that of QW under AlAs layer region. In case of annealing time being 120 sec, PL peak shift of QW under Al-oxide region is about 54 meV with compared to that of as-grown. Using the Fick's diffusion equation, modulation of QW shape after annealing was induced from the data of PL peak shifts. Diffusivity of QW under Al-oxide and AlAs region are about $1.3\sim 1.7\times 10^{-16cm^2/s$ and $0.5\sim0.9\times 10^{-16}cm^2/s$ respectively.
