Optical and electrical properties of boron-implanted amorphous germanium thin films

Abstract

Amorphous germanium films were implanted to high boron levels, ∼10²¹/cm³ peak concentrations. Before and after implantation the conductivity measurements fit the relation logσ∼T^−1/4 and no evidence of intravalence absorption was observed indicating that the Fermi level was near the center of the band gap. Thermoelectric power measurements indicated that the samples were weakly n type before implantation and p type after implantation. The position of the fundamental absorption edge shifted to lower energy upon implantation and to higher energies upon subsequent anneals. Implanted recrystallized films were strongly p type, exhibited intravalence absorption, and had very low dc activation energies.