Substitutional and Interstitial Doping of Amorphous Silicon Nitride

Abstract

AbstractDoped films of amorphous silicon nitride have been prepared by the glow discharge technique over a wide range of ammonia/silane mixtures. P- and B-doped specimens were produced by admixing phosphine or diborane during deposition. Interstitial doping was attempted by Na-ion implantation, and by in-diffusion of evaporated Li. For values of the ammonia/silane volume ratio R < 10−2, the optical gap remains unchanged and all the above dopants raise the room temperature conductivity to σRT ≅ 10−2(Ω cm)−1. With increasing R the efficiency of P, B and Na doping decreases rapidly. However, incorporation of Li continues to significantly increase σRT at higher R where the optical gap approaches 5eV. Near-stoichiometric, transparent specimens have been prepared with σRT increased by up to 14 orders of magnitude by Li doping. A discussion of the doping results is given.