Doping effects of group III elements to RF sputtered hydrogenated amorphous silicon

Doping effects of group III elements to hydrogenated amorphous silicon (a-Si:H) have been investigated using co-sputtering of poly-crystalline Si and dopant elements. Compared with gaseous doping of boron by glow discharge (GD) method, doping efficiency of Al and Ga by RF sputtering is smaller at lower doping concentrations (less than 0.5%), but at higher concentrations dark conductivity changes drastically more than 10 orders of magnitude, and high dark conductivity (10-1 ohm-1 cm-1) with low activation energy (0.02 eV) can be achieved. Optical band gap decreases with increasing doping concentration. (author)