MBE growth and in situ XPS characterization of silicon interlayers on (1 1 1)B surfaces for passivation of GaAs quantum wire devices

Abstract

In nanostructures, the surface-to-volume ratio is increased, and surface state problems become more serious, making success of the future III–V nanoelectronics strongly dependent on surface passivation. To solve this problem, we have been investigating a passivation scheme using a Si interlayer called Si interface control layer (Si ICL) [H. Hasegawa, Thin Solid Films 367 (2000) 58]. However, main efforts have been limited on (0 0 1) surfaces. This paper investigates the applicability of the Si ICL approach to (1 1 1)B surfaces. An ultrathin (1 nm) silicon layer was grown by MBE on GaAs and AlGaAs (1 1 1)B surfaces with (2×2), ( 19 × 19 ) and (1×1) surface reconstructions. Surfaces were characterized by in situ X-ray photoelectron spectroscopy (XPS) technique. Si layers grew epitaxially with Si–Ga bonds at the Si/GaAs interface and Si–As termination on top, suggesting surfactant roles played by As atoms. On nitridation of Si layer by nitrogen radicals at room temperature, Si–As bonds were replaced by Si–N bonds leading to partial nitridation of the Si layer. Unlike the case of the As-stabilized GaAs (0 0 1)-(2×4) surface, large reduction of band bending by 250–420 meV took place on (1 1 1)B surfaces, indicating large reduction of surface states. The results indicate effectiveness of the Si ICL passivation on (1 1 1)B surface.