2019年4月30日星期二

Interruption-assisted epitaxy of faceted p-InAs on buffered GaSb for terahertz emitters

We demonstrate molecular beam epitaxy growth of p-InAs layers on GaAs-buffered GaSb that may be suitable for terahertz applications. GaAs buffer deposition is initiated by applying growth interruption. Reflection high-energy electron diffraction shows that GaAs growth proceeds to a quasi-two-dimensional growth mode. The scheme allows growth of a p-InAs layer 600 nm to 1.0 µm thick. Growth performed without GaAs and growth interruption resulted in decomposition of the p-InAs. When the scheme is used, the ensuing p-InAs first follows quasi-two-dimensional growth before favoring faceted islanding. Under 800-nm-wavelength femtosecond laser excitation, the p-InAs layer generates terahertz signals 70% of that of bulk p-InAs.


Source:IOPscience

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2019年4月24日星期三

Bottom-up fabrication of InAs-on-nothing MOSFET using selective area molecular beam epitaxy

In this paper we report on the fabrication and electrical characterization of InAs-on-nothing metal-oxide-semiconductor field-effect transistor composed of a suspended InAs channel and raised InAs n+ contacts. This architecture is obtained using 3D selective and localized molecular beam epitaxy on a lattice mismatched InP substrate. The suspended InAs channel and InAs n+ contacts feature a reproducible and uniform shape with well-defined 3D sidewalls. Devices with 1 μm gate length present a saturation drain current (I Dsat) of 300 mA mm−1 at V DS = 0.8 V and a trans-conductance (GM ) of 120 mS mm−1 at V DS = 0.5 V. In terms of electrostatic control, the devices display a minimal subthreshold swing of 110 mV dec−1 at V DS = 0.5 V and a small drain induced barrier lowering of 50 mV V−1.


Source:IOPscience

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2019年4月18日星期四

Comparison of InAs quantum dots grown on GaInAsP and InP

We report on the growth of InAs quantum dots (QDs) on GaInAsP and InP buffers by metal–organic chemical vapour deposition on InP(100) substrates. Indium segregation and the As–P exchange reaction affect the QD nucleation and composition. The As–P exchange reaction has a more pronounced effect on the QDs grown on the InP buffer than on those grown on the GaInAsP buffer. A very thin (0.6 nm) GaAs interlayer grown between the buffer layer and the InAs QD layer consumes segregated indium and minimizes the As/P exchange reaction. Wavelength tuning from 1450 to 1750 nm covering the technologically important 1550 nm wavelength is also achieved for the InAs QDs grown with the thin GaAs interlayer.


Source:IOPscience

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2019年4月9日星期二

Proper In deposition amount for on-demand epitaxy of InAs/GaAs single quantum dots

The test-QD in-situ annealing method could surmount the critical nucleation condition of InAs single quantum dots or GaAs single quantum dots (SQDs) to raise the growth repeatability. Here, through many growth tests on rotating substrates, we develop a proper In deposition amount (θ) for SQD growth, according to the measured critical θ for test QD nucleation (θ c). The proper ratio θ/θ c, with a large tolerance of the variation of the real substrate temperature (T sub), is 0.964−0.971 at the edge and > 0.989 but < 0.996 in the center of a 1/4-piece semi-insulating wafer, and around 0.9709 but < 0.9714 in the center of a 1/4-piece N+ wafer as shown in the evolution of QD size and density as θ/θ c varies. Bright SQDs with spectral lines at 905 nm–935 nm nucleate at the edge and correlate with individual 7 nm–8 nm-height QDs in atomic force microscopy, among dense 1 nm–5 nm-height small QDs with a strong spectral profile around 860 nm–880 nm. The higher T sub in the center forms diluter, taller and uniform QDs, and very dilute SQDs for a proper θ/θ c: only one 7-nm-height SQD in 25 μm2. On a 2-inch (1 inch = 2.54 cm) semi-insulating wafer, by using θ/θ c = 0.961, SQDs nucleate in a circle in 22% of the whole area. More SQDs will form in the broad high-T sub region in the center by using a proper θ/θ c.


Source:IOPscience

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2019年4月3日星期三

First-principles density functional theory study of strained wurtzite InP and InAs

We report on semilocal and hybrid density functional theory study of strained wurtzite crystals of InAs and InP. The crystal-field splitting has a large and nonlinear dependence on strain for both crystals. Moreover, the study of the electronic deformation potentials reveals that the well-known quasi-cubic approximation fails to reproduce the electronic features of the non-ideal c/a ratio. This theoretical study is of crucial importance for the simulation of self-assembled InAs or InP nanowires.


Source:IOPscience

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