Enhanced surface passivation of GaAs nanostructures via an optimized SiO2 sol-gel shell growth

Gallium arsenide (GaAs) is an important compound semiconductor for optoelectronic devices. However, the fast nonradiative recombination velocity of GaAs requires surface passivation for the nano-optoelectronic and nanophotonic applications. Despite strides have been made in GaAs surface passivation, chemical treatments like sulfidation and nitridation suffer from reproducibility and stability issues, thus requiring protective layer encapsulation. Traditional vacuum based film passivation exposes samples to high temperature plasma, causing surface damage, and is expensive. Here, we demonstrate an effective passivation method via sol-gel growth of SiO2 shell on both dry etched GaAs nanopillar and bottom-up grown GaAs nanowires at room temperature with uniform coating and controlled thickness from sub-10 nm to around 100 nm, showing advantages in low cost as well as suitability for different types of nano morphology. X-ray photoelectron spectroscopy analysis confirms that the SiO2 sol-gel method with the addition of (NH4)2S can significantly remove the native oxides on the surface. Under the optimized SiO2 coating procedure, the emission intensity of dry etched GaAs nanopillar with a diameter of 0.5 μm is enhanced about 29.6 times and the decay lifetime of the minority carriers with a diameter of 1.8 μm increased from 43.6 to 477.5 ps. Thus, the easy fabrication, broad suitability, as well as effective passivation effect turn sol-gel growth of SiO2 into a cost-effective surface passivation approach for III–V nanostructures.