MODELING THE BASE CURRENT OF AN A-SIH/C-SI HETEROJUNCTION BIPOLAR-TRANSISTOR

The base current injected in the emitter of an a-Si: H/c-Si emitter base n-p-n HBT has an ideality factor quite dependent on the fabrication process. To analyze the origin of this effect we have developed a modeling of hole current density injected through the heterojunction and towards the amorphous emitter layer. This modeling is based on the numerical solution of Poisson's equation and the formulation of the current densities proposed by Rubinelli et al. in (1989). The fit of the experimental curves shows that the dominant parameter is the interface state density at the metallurgical junction directly dependent on the technological process.