  GaAs surface is characterized by a high density of surface states, which
preclude the utilization of this semiconducting material for the realization of
several advanced devices. Sulfur-based passivation has been found significantly
useful in reducing the effect of dangling bonds. In this article first, the
problem associated with GaAs surface has been discussed in a tutorial form.
Secondly, a brief introduction of a wide variety of surface passivation methods
was introduced. Sulfur passivation, the most effective surface state quenching
method, has been elaborated. Thirdly, current trends in the field of surface
passivation of GaAs surface have been discussed. Our discussion also focusses
on utilizing GaAs and alloys for the molecular electronics and molecular
spintronics and based on our insights in the GaAs (P. Tyagi, MRS Advances 2
(51), 2915-2920 2017) and molecular spintronics field ((P. Tyagi, D. F. Li, S.
M. Holmes and B. J. Hinds, J. Am. Chem. Soc. 129 (16), 4929, 2007) and P.
Tyagi, C. Riso, U. Amir, C. Rojas-Dotti and J. Mart\'inez-Lillo, RSC Advances
10 (22), 13006, 2020) ).
