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We report a detailed study on the valence band splitting in epitaxial lift-off (ELO) GaAs film bonded to silicon. The GaAs film used in this study was grown by molecular beam epitaxy on epiready GaAs (100) substrate. Variable temperature photoluminescence and reflectivity spectra were obtained for the as-grown film, the freestanding ELO film, and the ELO GaAs film bonded to silicon. The PL spectra for the GaAs film on Si showed the removal of the valence band degeneracy with the light hole and heavy hole transitions separated by 4.2meV at 10K and decreased monotonously to 1.6meV at 230K. No similar splitting was observed for the as-grown and freestanding films. The strain and stress were calculated at ε=(1.2±0.04)×10−3 and X=0.8±0.05kbar, respectively, at 10K and ε=(2.3±0.04)×10−4 and X=0.3±0.05kbar at 230K. The temperature dependence of the heavy hole–light hole separation energy indicated a strain-induced effect caused by the difference in the coefficient of thermal expansion between GaAs and Si. This shows the efficiency of using ELO techniques on dissimilar materials for strain related spectroscopy.

An output power of 2.5 W at a wavelength of 665 nm was obtained from a quantum-well (QW) and multipass-pumped AlGaInP-based vertical-external-cavity surface-emitting laser operated at a heat sink temperature of 10°C. Intracavity frequency doubling resulted in an output power of 820 mW at a wavelength of 333 nm. To the best of our knowledge, these are the highest continuous wave output powers from this type of laser both at the fundamental wavelength and in frequency-doubled operation. In fundamental wavelength operation, further power scaling by increasing the pump-spot size increased the output power to 3.3 W. However, at this power level, the laser was highly unstable. When the laser was operated at 50% pump duty cycle, a reproducible and stable peak output power of 3.6 W was obtained. These results demonstrate the potential of optical QW pumping combined with multipass pumping for the operation of AlGaInP-based semiconductor disk lasers.

Articles you may be interested inWell-width dependence of in-plane optical anisotropy in (001) GaAs/AlGaAs quantum wells induced by in-plane uniaxial strain and interface asymmetry Strain-induced splitting of the valence band in epitaxially lifted-off GaAs films Low temperature photoluminescence and reflectance measurements on epitaxially lifted-off ͑ELO͒ bulk GaAs and GaAs/AlGaAs multiple quantum wells ͑MQWs͒ bonded to Si and MgO substrates are reported. Photoluminescence measurements indicate no strain at room temperature for the ELO bulk GaAs film but show biaxial strain at 10 K. Si-bonded films undergo tensile strain, while films with MgO host substrates experience compressive strain. Reflectance measurements at 10 K show that light hole band is closer to the conduction band for the tensile strained film. In GaAs MQW ELO films, the separation of the heavy hole and light hole band is reduced in tensile strained films by 4.7 meV, corresponding to a strain = −0.7Ϯ 0.05ϫ 10 −3 and stress X = 0.9Ϯ 0.05 kbar ͑90Ϯ 5 MPa͒. For compressively strained films, this separation is enhanced by 3.9 meV, equivalent to a strain = 0.6Ϯ 0.05ϫ 10 −3 and X = 0.8Ϯ 0.05ϫ 10 −3 kbar ͑80Ϯ 5 MPa͒. The findings demonstrate that ELO is an effective technique to introduce tensile and compressive strain in GaAs heterostructures and is appropriate for strain-related spectroscopy.

Influences of the spacer layer growth temperature on multilayer InAs ∕ GaAs quantum dot structures