PHOTOLUMINESCENCE AND PHOTOTHERMAL DEFLECTION SPECTROSCOPY IN POTASSIUM-DOPED A-SI-H

Highly efficient n-type doping of a-Si:H films can be achieved by potassium implantation. Conductivities in the dark are two to four orders of magnitude larger than in the case of phosphorus doping. Moreover, an increase of up to a factor of four is detected when more hydrogen is introduced in the potassium doped samples. For high dose implantations (greater than or equal to 10(20) atoms/cm(3)), 1.3 eV spectral photoluminescence, carried out at 77 K, shows peaks of about a factor of three larger in potassium implanted films than in the phosphorus implanted ones at the same dose. If P and K implanted samples with the same electrical conductivity are compared, the same amount of disorder is detected by photothermal deflection spectroscopy measurements, but the photoluminescence of the K implanted samples is more than one order of magnitude higher in the K doped samples than in the P doped ones. The effect is tentatively interpreted in terms of dependence of photoluminescence quenching on total impurity concentration.