Analysis of stresses in GaAs waveguides integrated with ZnO thin films

Thin-film induced stress has been investigated on GaAs mesa structures integrated with ZnO films. ZnO films were sputter deposited on GaAs with a SiO 2 thin buffer layer. Stress on the cleaved facet of the GaAs mesa was imaged with a spatially-resolved and polarization- resolved photoluminescence technique. The result shows that the GaAs mesa is stressed up to 1 by 10 9 dyn/cm 2 (10 -3 strain) due to a residual compressive stress from the deposited films. A finite element analysis was also carried out to calculate the stress distribution. The simulation result shows a good agreement with the experimental result. As an application of the thin-film induced stress, we propose a new waveguide structure, in which vertical confinement of light is obtained via a photoelastic effect while lateral confinement is made by a mesa structure. A numerical analysis shows that the proposed waveguide structure can support vertical modes with the amount of thin-film induced stress observed in this work. The proposed structure can be fabricated on bulk semiconductor substrates without requiring any separate cladding layers for vertical confinement of light. The proposed structure, therefore, is promising for low propagation loss, 2-dimensional waveguides that can be formed with a simple and economical method.