Fabrication and characterization of in situ-doped a-Si sub(0.8)C sub(0.2) emitter bipolar transistors

Silicon-carbon emitters were deposited by plasma enhanced chemical vapour deposition (PECVD) on a conventional silicon transistor base. The resulting transistors were annealed after the emitter had been deposited which led to the dopant diffusing from the amorphous layer into the crystalline base. This paper analyses the effect of the annealing temperature on the properties of the amorphous layer and on the electrical characteristics of the transistors. First, after isochronal annealing between 740 degree C and 880 degree C, the physical properties of PECVD a-Si sub(0.8)C sub(0.2):H(n) layers were measured. Then, the base current of the transistors was analyzed as a function of the annealing temperature to gain deeper insight into its physical origin.