Abstract A novel n+-v-p+-v-n+ AlGaAs/GaAs heterojunction bipolar transistor (HBT) structure exhibiting negative differential conduction characteristics was successfully developed. Two types of device structures using a thin (10 nm) and a thick (100 nm) p+-GaAs base were studied. The current-voltage characteristics in the thin p+-base structure exhibit a new type of negative differential conduction (NDC) caused by an avalanche multiplication process. In the thick p+-base structure, the current-voltage characteristics are linear at 300 and 77 K, showing that the tunneling process dominates. The thin p+-base structure has shown good light sensitivity and good photoresponse speed. A simple NDC device-based circuit for high-speed logic was demonstrated and its electrical response speed was estimated.