  Current-voltage dependence is measured in (Ga,Sb)-doped ZnO up to 150 kV/cm
electric fields. A channel temperature is controlled by applying relatively
short (few ns) voltage pulses to two-terminal samples. The dependence of
electron drift velocity on electron density ranging from 1.42$\times$10$^{17}$
cm$^{-3}$ to 1.3$\times$10$^{20}$ cm$^{-3}$ at a given electric field is
deduced after estimation of the sample contact resistance and the Hall electron
mobility. Manifestation of the highest electron drift velocity up to
$\sim$1.5$\times$10$^{7}$ cm/s is estimated for electron density of
1.42$\times$10$^{17}$ cm$^{-3}$ and is in agreement with Monte Carlo simulation
when hot-phonon lifetime is below 1 ps. A local drift velocity maximum is
observed at $\sim$1.1$\times$10$^{19}$ cm$^{-3}$ and is in agreement with
ultra-fast hot phonon decay.
