  We introduce a solution for producing ultrashort ($\sim$fs) high charge
($\sim$pC) from ultra-compact guns utilizing single-cycle THz pulses. We show
that the readily available THz pulses with energies as low as 20 ?J are
sufficient to generate multi-10 keV electron bunches. Moreover, It is
demonstrated that THz energies of 2mJ are sufficient to generate relativistic
electron bunches with higher than 2 MeV energy. The high acceleration gradients
possible in the structures provide 30 fs electron bunches at 30 keV energy and
45 fs bunches at 2 MeV energy. These structures will underpin future devices
for strong field THz physics in general and miniaturized electron guns, in
which the high fields combined with the short pulse duration enable electron
beams with ultrahigh brightness.
