Multiple Switching Phenomena of AlGaAs/InGaAs/GaAs Heterostructure Transistors

An interesting multiple negative-differential-resistance (NDR) phenomenon is observed in AlGaAs/InGaAs/ GaAs heterostructure bipolar transistors with abrupt or graded AlGaAs confinement layers under the inverted operation mode. The switching behaviors are mainly due to avalanche multiplication and a two-stage barrier lowering effect. The switching properties of the first S-shaped NDR observed in the device with the abrupt confinement layer are better than those observed in the device with the graded confinement layer, due to the former device's superior confinement effect on holes and electrons. The control voltage efficiency of the second S-shaped NDR is nearly equal in the studied devices because the InGaAs quantum well dominates the properties of this NDR.