2019年5月28日星期二

Wafer-bonded coupled multilayer cavity with InAs quantum dots for two-color emission

A GaAs/AlAs coupled multilayer cavity structure with InAs quantum dots (QDs) was fabricated by wafer-bonding of two cavity structures grown individually. The wafer-bonding technique is important to control the spatial distribution of nonlinear polarization for strong terahertz emission by the differential frequency generation of the two cavity modes of the coupled cavity. Three layers of self-assembled InAs QDs were inserted in a cavity grown on a (001) GaAs substrate as optical gain materials for two-color emission of the cavity mode lights. The other cavity with a GaAs cavity layer was grown on a (113)B GaAs substrate. Two-color emissions with a 3.8 THz frequency difference were successfully observed from the wafer-bonded coupled cavity by cw optical pumping at room temperature.


Source:IOPscience

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2019年5月23日星期四

Effect of the growth mode on the two- to three-dimensional transition of InAs grown on vicinal GaAs(001) substrates

Some differences were observed between conventional molecular-beam epitaxy (MBE) and mobility enhanced epitaxy (MEE) of InAs on a vicinal GaAs(001) substrate in the variation of the number density N of the InAs islands, with additional InAs coverage (θ−θc) after the critical InAs coverage θc during the two- to three-dimensional (2D–3D) transition. For MBE the variation was consistent with the power law N(θ)~(θ−θc)α; while for MEE, the linear relation N(\theta) \propto (\theta-\theta_{\mathrm {c}})  was observed. The difference is discussed in terms of the randomness in the nucleation of the InAs islands.


Source:IOPscience

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2019年5月9日星期四

InSb quantum dots for the mid-infrared spectral range grown on GaAs substrates using metamorphic InAs buffer layers

Type II InSb/InAs quantum dots (QDs) were successfully grown on GaAs substrates using three different metamorphic buffer layer (MBL) designs. The structural properties of the resulting metamorphic InAs buffer layers were studied and compared using cross-sectional transmission electron microscopy and high resolution x-ray diffraction measurements. Photoluminescence (PL) originating from the InSb QDs was observed from each of the samples and was found to be comparable to the PL of InSb QDs grown onto homo-epitaxially deposited InAs. The 4 K PL intensity and linewidth of InSb QDs grown onto a 3 µm thick InAs buffer layer directly deposited onto GaAs proved to be superior to that from QDs grown onto an InAs MBL using either AlSb or GaSb interlayers. Light-emitting diode structures containing ten layers of InSb QD in the active region were subsequently fabricated and electroluminescence from the QDs was obtained in the mid-infrared spectral range up to 180 K. This is the first step towards obtaining mid-infrared InSb QD light sources on GaAs substrates.


Source:IOPscience


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