Three-dimensional tunneling in quantum ballistic motion

We provide an elementary case study of field-induced quantum tunneling in a realistic three-dimensional environment which exhibits both tunneling and classically allowed motion. An analytic description is presented for ballistic motion in a uniform electric field. From there we derive simple expressions concerning the wave function for field emission from an ultrathin quantum well in the tunneling limit. At the same time a wave-packet description of the tunneling process is obtained. The tunneling time can be read off from the lateral spread of the tunneling current distribution. (C) 1998 American Association of Physics Teachers.