GaAs metal-oxide-semiconductor device with titanium dioxide as dielectric layer: Effect of oxide thickness on the device performance

摘要

GaAs-based metal-oxide-semiconductor devices were fabricated with titanium dioxide (TiO_2) as an oxide layer having three different thicknesses of 33, 54 and 71 nm. The phase purity of TiO_2 was confirmed by Raman spectroscopy. Sulfur passivation on GaAs surface prior to TiO_2 deposition was proposed to suppress poor native oxide formation on GaAs. Frequency-dependent studies on the capacitance-voltage were made in the frequency range 10 kHz-1 MHz. It was found that within this frequency range dispersion of the oxide capacitance was 4.9% per decade. Electrical measurements exhibited low leakage current, a dielectric constant of ≈27 and an interface trap density (D_(it)) of ～10~(11) cm~(-2) eV ~(-1). Two orders of magnitude reduction in current density were observed as the temperature went down from 290 to 100 K. Flatband voltage (V_(FB)), dielectric loss tangent (tan φ) and ac conductivity (σ_(ac)) were determined from the capacitance-voltage (C-V) and conductance-voltage (G_P/ω-V) characteristics as a function of oxide thickness.