  An abrupt first-order metal-insulator transition (MIT) as a jump of the
density of states is observed for Be doped GaAs, which is known as a
semiconductor, by inducing very low holes of approximately n_p=5x10^{14}
cm^{-3} into the valence band by the electric field; this is anomalous. In a
higher hole doping concentration of n_p=6x10^{16} cm^{-3}, the abrupt MIT is
not observed at room temperature, but measured at low temperature. A large
discontinuous decrease of photoluminescence intensity at 1.43 eV energy gap and
a negative differential resistance are also observed as further evidence of the
MIT. The abrupt MIT does not undergo a structural phase transition and is
accompanied with inhomogeneity. The upper limit of the temperature allowing the
MIT is deduced to be approximately 440K from experimental data. The abrupt MIT
rather than the continuous MIT is intrinsic and can explain the "breakdown"
phenomenon (unsolved problem) incurred by a high electric field in
semiconductor devices.
