We have used photoluminescence of a GaAs/Al0.3Ga0.7As near-surface quantum
well structure to study the quality of the interface between GaAs and GaS d
eposited in ultrahigh vacuum (UHV) using [(Bu-t)GaS](4). In addition to the
luminescence of the near-surface and the deep/reference quantum wells, lum
inescence was observed for the GaAs cap following the deposition of 100 Ang
strom of GaS. This additional feature demonstrates the high quality GaS/GaA
s interface achievable through the UHV deposition of this precursor. The ra
tios of the integrated luminescence intensity of both the GaAs cap and the
near-surface GaAs quantum well to the deep/reference quantum well indicate
that there are fewer GaS/GaAs interface states for deposition on the Ga-ric
h GaAs(001)-(4 x 2)/(2 x 6) surface compared to deposition on the As-rich G
aAs(001)-(2 x 4) surface. Furthermore, GaS passivated samples exposed to am
bient conditions for eight months exhibit no luminescence degradation for t
he near-surface quantum well confirming that these films provide adequate p
assivation longevity. (C) 1999 American Institute of Physics. [S0003-6951(9
9)05147-5].