Selective and tunable red- or blue-shift emissions of GaAsP quantum well heterostructures

In this work we demonstrate tunable red- or blue-shift emissions of GaAs 0.9 P 0.1 quantum well (QW) heterostructures. The wavelength shift is achieved by ampoule sealed post-growth annealing of QW with different combinations of dielectric encapsulants and in various ambient conditions. For capless bare samples sealed in ampoules with little arsenic overpressure, furnace anneals at 800°C result in red photoluminescence (PL) shifts asymptotically as much as 75 meV with anneal time up to 40 hours. We attribute this redshift to the inter-diffusion of phosphorous and arsenic in QW and the neighboring confinement layers. For samples capped with a bilayer of SrF 2 and SiO x , similar temporal red shifts appear suggesting the combined dielectrics either prohibit or slow down the diffusion of column III vacancies during anneals. For samples capped with either SiO x or SiN x alone their PL spectra first shift toward longer wavelength then toward shorter wavelength. The large turn-around blue-shift (up to 165meV for 40hr annealing under 800°C) is attributed to the intermixing of Ga in QW and Al in the confinement layers. Additional complexity arises when As overpressure is replaced with Ga overpressure. For samples similarly capped with either SiO x or SiN x films, the turn-around blue-shift proceeds much faster (up to 281meV for only 5-hr annealing at 800°C). We attribute the slower blue-shift to the generation and diffusion of column III vacancies while the faster blue-shift to the kick-out of Zn-dopants in the heavily doped contact layer.