RESONANT-TUNNELING IN SEMI-METAL/SEMICONDUCTOR, ERAS/(AL,GA)AS, HETEROSTRUCTURES

Resonant tunneling appears in GaAs/AlAs/ErAs/AlAs/GaAs structures fabricated by MBE on (211)B, (311)B, (511)B and (100) semi-insulating substrates and ErAs thicknesses of 5, 10 and 15 monolayers. The resonant channel is essentially temperature independent, it dominates the background current and exhibits differential negative resistance only below 150 K. The exact nature of the resonant tunneling channel is made clear by magneto-tunneling experiments. Magnetic fields below 8 Tesla are sufficient to produce an anomalously large splitting of the resonant channel. This result is consistent with the known, large, Er 4f exchange enhanced, splitting of the conduction band in ErAs and implies that the resonant channel is a quantized electron state.