Ohmic contact is an important expression of the energy band change after metal-semiconductor contact. This paper summarizes the prerequisites and methods for achieving ohmic contact in the experimental process. This paper sums up in detail the several important factors affecting the formation of ohmic contact during the experimental process, including annealing temperature and time, epitaxial method, type of semiconductor contact layer and doping concentration, type and thickness of the metal contact layer, and size of the metal/semiconductor contact area, etc. We propose a simple and effective method to find the appropriate annealing temperature and time by determining the under-annealing and over annealing states of ohmic contact during the annealing process through a Ring Transmission Line Model. Through extensive experimental verification, the theoretical reasoning matches well with the experimental results. This has a tremendous role in Improving experimental efficiency.
We describe the temperature-dependence polarization properties of grating-gated AlGaN/GaN heterostructures at terahertz frequencies. Using the finite-difference time-domain method, it was demonstrated that as the temperature increases, the resonant frequency of the incident light was red-shifted. Simultaneously, a shorter gate length leads to a higher resonant frequency. In addition, at a lower temperature, the coupling efficiency of terahertz radiation and plasmon is higher. In our simulation results, the maximum modulation depth is 88%; at a gate length of 800 nm and lattice temperature of 77 K. For the same gate length, with higher electron gas concentrations and filling factor, greater modulation depths were produced. Studies on these properties may help in the design and optimization of terahertz detectors and modulators.
Additional scattering of electrons in the complex MOSFET channel caused by off-cut angle of (0001) 4H-SiC wafer, makes accurate crystal face acquisition much desired. Molten KOH was used to etch the circular grooves on the SiC wafer surface in muffle furnace, and hexagonal grooves with SiC crystal symmetry were obtained. Average etching rates at 500°C along <;11-20> and <1-100> direction were about 4.826 um/min and 4.112 um/min, respectively,with a etching anisotropy ratio of 1.18. The m face was obtained by controlling the etching time and Si face was obtained by selfstopping effect. The method we developed in this paper has potential applications in the accurate crystal face acquisition of (0001) 4H-SiC epi-wafer, and the preparation of structures based on 4H-SiC.
Localized plasmon modes are excited and probed in a large-area grating-gate GaN/AlGaN high-electron-mobility transistor structure embedded in a Fabry-Pérot cavity using a terahertz time-domain spectroscopy (THz-TDS) at cryogenic temperature. Determined by the length of grating finger and the electron concentration, the frequency of localized plasmon modes can be continuously tuned by the gate voltage in the spectral range from 0.1 THz to 1.5 THz. When the plasmon frequency is tuned to be in resonance with the terahertz Fabry-Pérot cavity mode, a strong coupling between the plasmon mode and the cavity mode is observed and the terahertz plasmon-polaritons are formed in such a cavity-coupled two-dimensional electron system. The electromagnetic simulations have confirmed the strong coupling between them.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.