NONUNIFORM DISTRIBUTION OF STRAIN IN INGAAS/GAAS QUANTUM WIRES

Nonuniform strain distribution in In0.2Ga0.8AsGaAs strained quantum wire (QWR) has been observed by measuring the lattice spacing from the high-resolution transmission electron microscopic lattice image of the cross section of the wire. It was found that in the wire, the region near the wire sidewall was under a larger compressive strain in the growth direction (vertical strain) than the center of the wire. In the barrier, near the wire sidewall, GaAs was under a vertical tensile strain by the In0.2Ga0.8As wire. This observation explains experimental observation of quantum confinement in strained InGaAs/GaAs quantum wires where the possibility of nonconfining band offsets was previously hypothesized. This phenomenon of nonuniform vertical strain distribution in the wire is essential for the application of these strained material systems to the fabrication of strained QWR lasers, and the result presented here is important for the further modeling and design of these strained QWR structures.