Amorphous silicon ͑a-Si͒ networks have been generated from melted Si with various quenching rates by molecular-dynamics ͑MD͒ simulations employing the Tersoff potential. The cooling rates were set between 5ϫ10 11 and 1ϫ10 14 K/s; the latter is the slowest quenching rate in MD simulations previously performed. Although the atomic configurations formed by the cooling rate of 10 14 K/s could reproduce the radial distribution function of a-Si obtained experimentally, they contained numerous structural defects such as threefoldand fivefold-coordinated atoms. As the cooling rate decreased, the average coordination number became Ϸ4 and tetrahedral bonds predominated. The structural and dynamical properties of a-Si generated by a cooling rate with ϳ10 12 K/s were in excellent agreement with those of a-Si obtained experimentally.
Precise control of dopant composition is critical for the production of semiconductor films with desired properties. Here, we present results on the electrical properties for Si doped Ga2O3 films grown by pulsed laser deposition technique (PLD). The Si composition in the films can be controlled by changing the target composition as observed from the secondary ion mass spectroscopy measurement. The carrier density of the films is varied from the order of 1015 to 1020 cm−3 while the conductivity from 10−4 to 1 S cm−1 as measured by Hall equipment. The carrier density of the films has been verified by Kelvin force microscopy, which shows an increased surface work function with the increase of carrier density. The results suggest that the carrier density of β-Ga2O3 films is controllable by Si doping by PLD, paving a way to develop the Ga2O3 film-based electronic devices.
Structural and dynamical properties of liquid Si ͑l-Si͒ have been investigated by molecular-dynamics calculations using the Tersoff potential. The pair-correlation function g(r), bond-angle distribution function g͑͒, and velocity autocorrelation function Z(t) were calculated and compared with those of l-Si generated by the Stillinger-Weber ͑SW͒ potential and ab initio calculations reported previously. The Tersoff liquid reproduces g(r) obtained by the SW potential and ab initio calculations except for a slight quantitative difference. On the other hand, g͑͒ of the Tersoff liquid is entirely different from that of the SW liquid, but it is similar to the result of the ab initio approach. These results suggest that the Tersoff potential describes the features of static structures of l-Si, though this potential overestimates greatly the melting point. The Tersoff potential yields a similar tendency to the dynamical properties obtained by ab initio simulation, but some discrepancies exist, e.g., the period of oscillation in Z(t).
We propose a novel resonant detector of terahertz radiation based on a heterostructure with an ungated two-dimensional electron channel, with a lateral Schottky junction at one of the channel edges, substantiate its operation, and evaluate the device characteristics. We demonstrate that the detector responsivity can exhibit sharp resonant maxima at the frequencies pertaining to the plasma oscillations. As shown, the peak values of the responsivity of the detector proposed can exceed the responsivity of the standard Schottky detectors by several orders of magnitude if the electron mobility in the channel is sufficiently high.
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