Oxide-confined GaAs-based vertical-cavity surface-emitting laser: Measurement and modeling of the strain field

The strain field of the emitters of one unstressed and two electrically stressed oxide-confined GaAs-based vertical-cavity surface-emitting lasers has been analyzed. The components of the strain tensor in the optical aperture, in the quantum wells, and at the oxide edge of the lamellas have been measured by nano-beam precession electron diffraction and geometrical phase analysis. The measurements have been used to validate the simulations based on the finite element method (FEM) of the mechanical behavior of the emitters. The FEM model is used to quantify the strain caused by the lattice mismatch of the GaAs-based epitaxial layers and the volume variation of the Al 98Ga 2As layer due to selective oxidation. The first is calculated as a function of the misfit strain and corresponds very well to the measured values. The latter is calibrated assuming that the thickness of the oxide is expanded by 4 % in both the unstressed sample and the stressed sample with dislocations. Instead, it is contracted by 8 % for the sample where the stress test has caused further oxidation.