MAGNETOTUNNELING AND MAGNETIC FREEZEOUT IN n** minus GaAs-UNDOPED Al//xGa//1// minus //xAs minus n** plus GaAs CAPACITORS.

We have reported the observation of a remarkable periodic structure in the current-voltage (I-V) curves of n** minus GaAs-undoped Al//xGa//1// minus //xAs minus n** plus GaAs capacitors at 1. 6 K in the presence of high magnetic fields. Results were presented for samples oriented perpendicular to the direction of the magnetic field; sixteen periods are observed in this case. We present here results for a sample oriented parallel to the magnetic field; at least thirty periods can be observed for minus 1. 2 V less than V//G less than O V where V//G is the voltage applied to the n** plus GaAs gate. Periodic structure is also seen in capacitance-voltage (C-V) characteristics of SIS capacitors. The mechanism appears to involve sequential LO phonon emission events by ballistic electrons.