Interfacial Electrical Properties of MBE-Y2O3/GaAs MOS capacitors

• Main Authors: Su, Yu Kai, 蘇毓凱
• Other Authors: Hong, M.
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/43961406293095296506

碩士 === 國立清華大學 === 材料科學工程學系 === 101 === The scaling of Si-based MOSFETs is approaching limitation, GaAs has highly potential to be a candidate for n-channel MOSFETs. MBE-Y2O3 as gate dielectric on GaAs attracts our attention because of its high dielectric constant of ~16, relatively high band offset, high thermodynamic stability, and possibility of formation sharp interface with low Dit value. In-situ MBE-Y2O3 on p- and n-GaAs without using interfacial passivation layers and chemical treatments between oxide/GaAs interface were performed in a multi-chamber UHV-MBE system. The MOSCAPs of MBE-YAO/MBE-Y2O3/GaAs were initially post deposition annealed at 900oC for 60s in nitrogen ambient followed by post metallization annealing at 400oC for 5 minuet in forming gas, which has shown small frequency dispersion 4.6% (100Hz-1MHz) at accumulation region for p-MOSCAPs, and 12.4% for n-MOSCAPs. Further, the Dit(E) spectra within the GaAs band gap were extracted by applying Terman, QSCV, temperature-dependent conductance methods for MBE-YAO/MBE-Y2O3/GaAs MOSCAPs. The Dit’s extracted from QSCV exhibits a V-shaped Dit(E) distribution without discernible peak. The Dit near midgap is given by ~1×10^12 eV^(-1)cm^(-2), and high D_it~1×10^13 eV^(-1)cm^(-2) located at near conduction and valence band edge are observed. The Dit’s extracted from temperature-dependent conductance method gives D_it~3-5×10^11 eV^(-1)cm^(-2) lying 0.4-0.6 eV above the valence band edge. Moreover, the inversion-like humps, which is an indication of Dit(E) peak feature causing insufficient Fermi-level movement, are not observed in QSCV measurement and high-temperature (373K) C-V characteristics. The study shows the high potential of MBE-Y2O3/GaAs system to realize enhance mode MOSFETs due to its low Dit in midgap region and excellent thermodynamic stability after RTA to 900oC for S/D activation.