High-resolution x-ray diffraction has been used to analyze the type and density of threading dislocations in a series (0001)-oriented GaN epitaxial film. Photoluminescence (PL) and carrier mobility of the films are measured at room temperature. The intensities of both the band edge (3.42 eV) peak and yellow luminescence (YL) are strongly related to the threading dislocation density of the GaN films. But different types of dislocations show different relationship with the intensities of PL and YL. The fundamental correlation is found not only between the interaction of edge- and screw-type dislocations and the carrier mobility but also between the interaction and the intensities of both the band edge peak and the YL.
In this letter, the authors present the capacitance-voltage and current-voltage characteristics of TaN∕HfO2∕n-GaAs metal-oxide-semiconductor capacitors with thin silicon and germanium interfacial passivation layers (IPLs). Physical vapor deposition high-k dielectric films and silicon/germanium IPLs were deposited on GaAs substrate which has been cleaned with HCl and (NH4)2S solutions. Equivalent oxide thickness (EOT) of 12.5Å and dielectric leakage current density of 2.0×10−4A∕cm2 at ∣VG−VFB∣=1V with low capacitance-voltage frequency dispersion have been obtained. The results indicate that the use of a thin silicon/germanium IPL assists in scaling EOT below 13Å, while improving the quality of the interface.
We present the capacitance-voltage characteristics of TaN∕HfO2∕n-GaAs metaloxide-semiconductor capacitors, with an equivalent oxide thickness (EOT) of 10.9Å, low frequency dispersion, and a low leakage current density (Jg) of ∼10−6A∕cm2 at ∣VG−VFB∣=1V. Physical vapor deposited high-k dielectric film (HfO2) and a thin germanium (Ge) interfacial control layer (ICL) were used to achieve the low EOTs. As postdeposition annealing (PDA) time increases beyond a critical point, EOT and Jg also abnormally increase due to the degradation of the interface between Ge and GaAs surface, which was well indicated in electron energy loss spectroscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy analyses. Results indicate that a thin Ge ICL, optimized conditions for PDA, as well as high-k material (HfO2) play important roles in allowing further EOT scale down and in providing a high-quality interface.
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