The linewidth enhancement factors of lattice-matched 1.5 µm wavelength InGaNAs/GaAs and InGaAs/InP singlequantum-well structures have been calculated using microscopic theory including many-body effects and a 10x10 effective-mass Hamiltonian.For applications which require high gain and carrier densities, InGaNAs/GaAs quantum wells have a much lower linewidth enhancement factor over a temperature range 300-400 K than InGaAs.The linewidth enhancement factor of InGaNAs is almost independent of both carrier density and temperature compared with InGaAs.The small-signal modulation characteristics of these 1.5µm lattice-matched structures and their temperature dependence have also been calculated.It is found that the maximum bandwidth of the InGaNAs/GaAs quantum well lasers is about 2.3 times larger than that of the InGaAs/InP quantum well lasers due to the high differential gain.The slope efficiency for the 3dB bandwidth as a function of optical density is twice as large for InGaNAs/GaAs as for InGaAs/InP quantum well lasers.
We demonstrate a high-performance photodetector with multilayer tin diselenide (SnSe2) exfoliated from a high-quality crystal which was synthesized by the temperature gradient growth method. This SnSe2 photodetector exhibits high photoresponsivity of 5.11 × 105 A W-1 and high specific detectivity of 2.79 × 1013 Jones under laser irradiation (λ = 450 nm). We also observed a reproducible and stable time-resolved photoresponse to the incident laser beam from this SnSe2 photodetector, which can be used as a promising material for future optoelectronic applications.
Highly conductive and water-dispersible sheets of reduced graphene oxide (RGO) were produced by rapidly heating graphene oxide (GO) paper at a low temperature (300 °C) for a short processing time of 3 s. The GO paper was thermally treated during the rapid-heating reduction process and, consequently, the oxygen functional groups in the obtained RGO were highly reduced. The RGO film displays good thermal stability, crystallinity, low sheet resistance, and good dispersibility in water, which makes it an ideal candidate to be used in various carbon-based electronic devices. We finally demonstrate the suitability of RGO as an active channel material and as a source-drain electrode for graphene field-effect transistors, which bring the possibility of realizing all-carbon devices a step closer to reality.
Abstract Diode characteristics of transition metal dichalcogenides are studied extensively owing to their electrical and optical properties. In particular, the Schottky barrier diode (SBD) structure has advantages, such as its small leakage current and power consumption, over conventional p–n diodes. This study develops an SBD system using n‐type tungsten disulfide (WS 2 ). By depositing a low work function In ( Φ In = 4.1 eV) and high work function Au ( Φ Au = 5.1 eV) on n‐type WS 2 , the diode characteristics are demonstrated to be close to an ideal diode. The In–Au contacts are measured, and SBD characteristics are confirmed with a 1.02 ideality factor at a zero back‐gate voltage at room temperature and a rectification ratio up to 5 × 10 2 , even at a low temperature (77 K), indicating almost ideal diode properties. In addition, the In electrodes exhibited improved electrical properties, with a high on/off ratio of 10 7 , mobility that is 100 times higher, and Schottky barrier height that is 20 times lower than that of Au electrodes.
Magnetoresistance and temperature-dependent conductance are measured in the sample made of a GaAs/Al${}_{x}$Ga${}_{1\ensuremath{-}x}$As quantum well with self-assembled InAs dots. Conductance is analyzed by Mott's hopping theory; the localization lengths have been extracted at various gate voltages. The sample is in the transition from near to metal-insulator to the deeply hopping regime with the combined effect of the long- and short-range scattering potentials. The magnitude of the negative magnetoresistance increases with increasing negative gate voltage. The magnetic-field dependence of the resistance can be explained by the theory of the interference model of hopping electrons.
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