  Advancement of optoelectronic and high-power devices is tied to the
development of wide band gap materials with excellent transport properties.
However, bipolar doping (n-type and p-type doping) and realizing high carrier
density while maintaining good mobility have been big challenges in wide band
gap materials. Here P-type and n-type conductivity was introduced in
beta-Ga2O3, an ultra-wide band gap oxide, by controlling hydrogen incorporation
in the lattice without further doping. Hydrogen induced a 9-order of magnitude
increase of n-type conductivity with donor ionization energy of 20 meV and
resistivity of 10-4 Ohm.cm. The conductivity was switched to p-type with
acceptor ionization energy of 42 meV by altering hydrogen incorporation in the
lattice. Density functional theory calculations were used to examine hydrogen
location in the Ga2O3 lattice and identified a new donor type as the source of
this remarkable n-type conductivity. Positron annihilation spectroscopy
confirmed this finding and the interpretation of the results. This work
illustrates a new approach that allows a tunable and reversible way of
modifying the conductivity of semiconductors and it is expected to have
profound implications on semiconductor field. At the same time it demonstrates
for the first time p-type and remarkable n-type conductivity in Ga2O3 which
should usher in the development of Ga2O3 devices and advance optoelectronics
and high-power devices
