A NEW TECHNIQUE FOR DIRECTLY PROBING THE INTRINSIC TRISTABILITY AN DITS TEMPERATURE-DEPENDENCE IN A RESONANT-TUNNELING DIODE

A new measurement technique employing a positively sloping load line h as been used to probe the region of apparent bistability near a tunnel ing resonance in the electrical characteristic of a resonant tunneling diode. This technique is equivalent to using a voltage source and neg ative series resistance. The appearance of bistability is an artifact of the conventional measuring technique which uses a load line with ne gative slope. The complete characteristic is found to be a continuous Z shaped curve between 20 and 150 K, corresponding to tristability and in accordance with theoretical models based on the effects of charge accumulation in the central quantum well of the diode. The width of th e tristable region passes through a maximum at 40 K and, at 150 K, dis appears as the resonance broadens. Above this temperature the resonanc e develops a region of negative differential resistance (NDR). As the device is cooled below 20 K additional structure develops in the centr al arm of the Z, with some portions of the characteristic exhibiting f ive stable current states at temperatures below 15 K. At 4.2 K, the ef fect of an in plane magnetic field mimics that of increasing temperatu re.