Passivation of GaAs (001) surfaces by forming Si and GaN interface control layers on Ga-rich (4×6) surface

摘要

This paper demonstrates that completely pinning-free surface passivation of (001) GaAs surfaces can be realized by forming Si and GaN ICLs on the untraditional Ga-rich (4 × 6) surface. Cubic (c-) GaN ICL was formed by direct nitridation of GaAs surface using N-radicals, followed by deposition of a SiN{sub}x film. Si ICL was grown by MBE, followed by its partial nitridation using N-radicals to form a thin SiN{sub}x layer. As a main passivation dielectric, a thick SiO{sub}2 dielectric film was deposited subsequently by rf-CVD. After forming Si and c-GaN film on the (4 × 6) surfaces, in-situ UHV STS on these surfaces indicated a dramatic reduction of surface states. UHV PL intensity for GaAs band-edge emission became 10 times larger than that of the As-rich (2 × 4) surface. MIS C-V measurements in air on MIS capacitors having Al/SiO{sub}2/SiN{sub}x/Si ICL/(4 × 6) GaAs and Al/SiO{sub}2/SiN{sub}x/c-GaN ICL/(4 × 6) GaAs structures showed complete unpinning of Fermi level over the entire energy gap of GaAs. Thus, excellent interface properties in UHV conditions could be successfully maintained to air-exposed practical MIS structures, giving N{sub}(SSmin) values of 1 × 10{sup}(10) and 4 × 10{sup}(10) cm{sup}(-2)eV{sup}(-1) for c-GaN ICL and Si ICL structures, respectively.