The helicon-wave-excited-plasma sputtering (HWPS) method was exemplified to be one of the versatile epitaxial growth techniques for the fabrication of low dislocation density semiconductor epilayers and heterostructures exhibiting atomically smooth surface morphology. For a case study, ZnO homoepitaxy and MgxZn1−xO (x=0.08,0.19) heteroepitaxy on a Zn-polar ZnO substrate were carried out. According to the surface damage-free property, high temperature growth with appropriate stoichiometry control enabled the growth of ZnO homoepitaxial layers exhibiting a smooth surface morphology with 0.26 nm high monolayer atomic steps. Their tilt and twist mosaics reflecting the threading dislocation densities having screw and edge components were comparable to those of the substrate, being under the resolution limit (18 arcsec). The surface morphology and crystal mosaicity of pseudomorphic MgxZn1−xO (x≤0.19) epilayers were quite similar to those of the ZnO underlayer. The luminescence spectra of the ZnO and MgxZn1−xO epilayers at 293 K exhibited a predominant near-band-edge emission and negligible broad emission bands due to deep levels. The results indicate that the growth mode of the HWPS method resembles that of molecular beam epitaxy methods.
The helicon-wave-excited-plasma sputtering epitaxy (HWPSE) method was exemplified to grow atomically-smooth semiconductor epilayers of good structural and optical qualities. For a case study, ZnO homoepitaxy was carried out. According to the surface damage-free nature, the Zn-polar ZnO epilayers grown above 950 °C exhibited a smooth surface morphology with 0.26-nm-high monolayer atomic steps, of which tilt and twist mosaics were comparable to those of the substrate. Their room temperature photoluminescence (PL) spectrum was dominated by the free-excitonic emission. Clearly split PL peaks originating from A-exciton polaritons and sharp peaks due to the first excited-state excitons were observed at low temperature.
A GaInNAs/GaAs five-layer asymmetric coupled quantum well (FACQW) in the 1.3-mm-wavelength region was proposed and theoretically analyzed. The valence band structures of the FACQW were analyzed using the Luttinger-Kohn Hamiltonian based on the k Á p perturbation theory and a nonvariational method. The GaInNAs/GaAs FACQW can exhibit a unique behavior of the quantum confined Stark effect, leading to a large electrorefractive index change (Án=ÁF ¼ 3:9 Â 10 À4 cm/kV) at a small electric field in a wide-transparencywavelength region far from the absorption edge. This characteristic is comparable to InGaAs/InAlAs and InGaAsP FACQWs operated in the 1.55-mm-wavelength region. The GaInNAs/GaAs FACQW is expected to realize ultrawide-band, ultrafast optical modulators and switches and other functional devices based on the phase shift in the 1.3-mm-wavelength region. The driving voltage of a 1 mm-phase modulator is estimated to be 0.4 V. #
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.