  Silicon-based tracking detectors have been used in several important
applications, such as in cancer therapy using particle beams, and for the
discovery of new elementary particles at the Large Hadron Collider at CERN.
III-V semiconductor materials are an attractive alternative to silicon for this
application, as they have some superior physical properties. They could meet
the demands for fast timing detectors allowing time-of-flight measurements with
ps resolution while being radiation tolerant and cost-efficient. As a material
with a larger density, higher atomic number Z and much higher electron mobility
than silicon, GaAs exhibits faster signal collection and a larger signal per
{\mu}m of sensor thickness. In this work, we report on the fabrication of
n-in-n GaAs thin-film devices intended to serve next-generation high-energy
particle tracking detectors. Molecular beam epitaxy (MBE) was used to grow
high-quality GaAs films with doping levels sufficiently low to achieve full
depletion for detectors with an active thickness of 10 {\mu}m. The signal
collection speed of the detector structures was assessed using the transient
current technique (TCT). To elucidate the structural properties of the
detector, Kelvin probe force microscopy (KPFM) was used, which confirmed the
formation of the junction in the detector and revealed residual doping in the
intrinsic layer. Our results suggest that GaAs thin films are suitable
candidates to achieve thin and radiation-tolerant tracking detectors.
