Doping effects on variable optical band gap amorphous silicon nitride compounds

Doping effects were studied in variable band-gap a-SiN(x):H. The material is potentially useful for the window side of a-Si:H p-i-n solar cells. Samples produced in a capacitively coupled glow discharge system were prepared from a gaseous mixture of SiH4 and N2. Maintaining identical growth parameters, the optical band gap can be varied in a continuous way by changing the RF power delivered to the plasma. The present experiments show that changes in conductivity and photoconductivity depend: (1) on the nature of the dopant gas, (2) dopant concentration and (3) the relative nitrogen content in the network. The differences appearing between boron and phosphorus doping are explained in terms of different bonding configuration for both atoms.