A new GaAs switching device with a triple‐well superlattice emitter structure, prepared by molecular beam epitaxy, has been fabricated and demonstrated. An S‐ and N‐shaped negative‐differential‐resistance (NDR) phenomenon, attributed primarily to the avalanche multiplications process and resonant‐tunneling effect, were observed simultaneously when a proper collector‐emitter voltage (VCE) was applied. The operation temperature is known from the experimental results to play an important role on the influence of the NDR behaviors. A transistor action with a common‐emitter current gain of over 36 was also achieved at 300 K when a control current was employed to the base electrode. This device exhibited a significantly regenerative switching phenomenon both at room temperature and low temperature if a −VCEvoltage was used. The proposed structure consequently has good potential for switching and quantum functional device applications.