ZnO and Y-doped ZnO nanocrystalline films were separately fabricated on the glass substrates by sol-gel spin-coating method. X-ray diffraction patterns of the films show the same wurtzite hexagonal structure and (002) preferential orientation. SEM images show that grain size and thickness of the nanocrystalline films decrease with increasing doping concentration. The decrease of optical bandgap with the increase of Y doping is deduced from the transmittance spectra. Temperature-dependent resistivity reveals a semiconductor transport behavior for all ZnO and Y-doped ZnO nanocrystalline films. The resulting conductivity originates from the combination of thermal activation conduction and Mott variable range hopping (VRH) conduction. In the high temperature range, the temperature-dependent resistivity can be described by the Arrhenius equation, σ(T)=σ 0 exp[-(E a /kT)], which shows the thermal activation conduction. The activation energy E a increases from 0.47 meV for ZnO film to 0.83 meV for Zn 0.98 Y 0.02 O film. On the contrary, in the low temperature range, the temperature-dependent resistivity can be fitted well by the relationship, σ(T)=σ h0 exp[-(T 0 /T) 1/4 ], which indicates the behavior of Mott VRH. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the ZnO and Y-doped ZnO nanocrystalline films are affected by Y doping.
Microwave annealing (MWA) activates dopants through solid-phase epitaxial regrowth with low thermal budget. Optimizing the microwave power during MWA is capable of realizing low defect density at the junction, suppressing the dopant diffusion, and mitigating the straggle effect of ion implantation. These favorable features of MWA facilitate the formation of extremely abrupt junction profiles in tunnel FETs (TFETs). In conjunction with the improved gate-to-channel controllability of the multiple-gate (MG) structure, we demonstrate high-performance lateral n-type Si-TFETs using a CMOScompatible process flow with excellent band-to-band tunneling efficiency and device scalability. The 32-nm MG Si-TFET shows promising characteristics, including a high ON-state current of 41.3 µA/µm, a large current ON/OFF ratio of >5 × 10 7 , and minimal short-channel effect using V G = 2 V and V D = 1 V. Index Terms-Microwave annealing (MWA), solid-phase epitaxial regrowth (SPER), tunnel FET (TFET).
In recently years, high-index-contrast semiconductor ring and disk resonators have attracted much attention.Nanofabrication techniques now allow the realization of semiconductor microcavity ring and disk resonators with evanescent wave coupling to submicron-width waveguides across submicron-width air gaps. In this paper, we use the finite-difference time-domain (FDTD) method to simulate the coupling efficiencies and resonant frequencies for optical microcavity ring and disk resonators devices. Studies of the transmission characteristics illustrate the transition from single-mode resonances to whispering-gallery-mode resonances as the waveguide width of the micro-ring approaching to a fulfilled micro-disk.
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