  Gallium Arsenide and related compound semiconductors lie at the heart of
optoelectronics and integrated laser technologies. Shaped at the micro and
nano-scale, they allow strong interaction with quantum dots and quantum wells,
and promise to result in stunning devices. However gallium arsenide optical
structures presently exhibit lower performances than their silicon-based
counterparts, notably in nanophotonics where the surface plays a chief role.
Here we report on advanced surface control of miniature gallium arsenide
optical resonators, using two distinct techniques that produce permanent
results. One leads to extend the lifetime of free-carriers and enhance
luminescence, while the other strongly reduces surface absorption originating
from mid-gap states and enables ultra-low optical dissipation devices. With
such surface control, the quality factor of wavelength-sized optical disk
resonators is observed to rise up to six million at telecom wavelength, greatly
surpassing previous realizations and opening new prospects for Gallium Arsenide
nanophotonics.
