In-situ X-ray photoelectron spectroscopy characterization of Si interlayer based surface passivation process for AlGaAs/GaAs quantum wire transistors

摘要

Detailed properties of the Si interface control layer (Si ICL)-based surface passivation structure are characterized by in-situ X-ray photoelectron spectroscopy (XPS) in an ultra-high vacuum multi-chamber system. Si ICLs were grown by molecular beam epitaxy (MBE) on GaAs and AlGaAs(OOl) and (111)B surfaces, and were partially converted to SiN_x by nitrogen radical beam. Freshly MBE-grown clean GaAs and AlGaAs surfaces showed strong Fermi level pinning. Large shifts of the surface Fermi level position corresponding to reduction of pinning took place after Si ICL growth, particularly on (111)B surface (around 500 meV). However, subsequent surface nitridation increased pinning again. Then, a significant reduction of pinning was obtained by changing SiN_x to silicon oxynitride by intentional air-exposure and subsequent annealing. This has led to realization of a stable passivation structure with an ultrathin oxyni-tride/Si ICL structure which prevented subcutaneous oxidation during further device processing under air-exposure. The Si-ICL-based passivation process was applied to surface passivation of quantum wire (QWR) transistors where anomalously large side-gating phenomenon was completely eliminated.