The effect of deposition procedure on the conductivity of hydrogenated amorphous silicon multilayer films

The conductivity of multilayer P-doped amorphous hydrogenated silicon (a-Si:H) thin films is measured for films prepared with different deposition procedures. Multilayer films are deposited by plasma enhanced CVD following a procedure in which the plasma is extinguished and the deposition chamber is filled with air or argon after the deposition of each layer. These films are compared to films grown in continuous deposition runs. The technique provides a direct means to determine the effects of continuous versus interrupted deposition and to analyze oxide interface and bulk gap state densities. Exposing the layers to air between depositions produces deleterious effects whereas the effect of argon exposure are slight. Literature values for the density of states in oxidized a-Si:H are used to provide evidence for a defective layer in very thin P-doped a-Si:H having a defect density of over 10/sup 13/ cm/sup -2/ eV/sup -1/ approximately 0.3 eV below the transport level