  The detection of GRB 180722B and GRB 190114C in sub-TeV gamma-rays has opened
up a new window to study gamma-ray bursts in high energy gamma-rays. Recently
it is shown that the synchrotron and inverse Compton processes are responsible
for the production of these high energy gamma-rays during the afterglow. Here,
for the first time we demonstrate that, the photohadronic scenario which is
successful in explaining the multi-TeV flaring in high energy blazars is also
applicable for gamma-ray bursts. We show that the sub-TeV spectra of GRB
190114C and GRB 180720B are due to the interaction of high energy protons with
the background photons in the synchrotron self-Compton region and synchrotron
region respectively. The nature of the background photon distributions help us
to constraint their bulk Lorentz factors.
