Atomic layer deposited Al₂O₃ on high quality p-type epitaxial-GaAs/Ge for advanced III-V/Ge based device application

Development of high quality p-type epitaxial gallium-arsenide (epi-GaAs) on germanium (Ge) with sub-nm surface roughness is much sought after for the next generation high speed transistors application. High quality zinc doped p-type epitaxial GaAs with surface roughness of ~0.87 nm was grown on Ge substrates at 675 °C. Thin Al_0.3Ga_0.7As buffer layer and un-doped GaAs of 300 nm thick were introduced to suppress the Ge defects and auto-doping into epi-GaAs layer. The material and optical properties of the p-type epi-GaAs/un-doped GaAs/Al_0.3Ga_0.7As/Ge structures were examined through PL and Raman analysis. The metal-oxide-semiconductor capacitor (MOSC) was fabricated using p-type epi-GaAs layer and atomic-layer-deposited Al₂O₃ gate dielectric. The effective dielectric constant of the Au/Al₂O₃/p-epi-GaAs gate-stack is 5.9 and hysteresis voltage of 500 mV was observed. The epi-GaAs layer is p-type in nature with doping densities of 5×10¹⁷ cm^-3.