Application of SiO₂ aerogel film for interlayer dielectric on GaAs with a barrier of Si₃N₄

Si₃N₄ film was adopted as a barrier layer for SiO₂ aerogel/GaAs system. Si₃N₄/GaAs formed an almost chemically sharp interface and nearly maintained their chemical inertness during in-situ heating until 400 °C under ultra high vacuum condition. One micrometer thick SiO₂ aerogel film was prepared on the Si₃N₄/GaAs system using supercritical drying procedure at 250 °C and under 1160 psi. The thickness of Si ₃N₄ barrier layer was varied as 400, 600 and 900 Å. The dielectric constant of all SiO₂ aerogel/Si₃N ₄/GaAs system was measured as approximately 1.9 and almost no difference was observed from the changes in the thickness of Si ₃N₄ barrier layer. The leakage current densities were measured as low as under 2×10^-7 A/cm² and these values are two orders smaller than that of SiO₂ aerogel/GaAs system prepared without the introduction of Si₃N₄ barrier layer. All the aerogel/Si₃N₄/GaAs systems show ohmic conduction at low applying field and space charge limited conduction at high applying field. Furthermore, a reduced leakage current behavior was observed with increased Si₃N₄ layer thickness and could be explained from the electric-field depression effect due to accumulated charges in the films.