Optimization of the as-deposited 1.54 μm photoluminescence intensity in a-SiOx:H⟨Er⟩

Erbium-doped a-Si:H has Er3+-related photoluminescence (PL) at similar to 1.54 mu m (similar to 0.8 eV). This emission is an intra-4f level transition of the Er3+ ion: which can be increased by adding O. In this paper we present a study of the dependence of the Er3+ luminescence on Er and O concentration ([Er] and [O]) in a-SiOx:H. Samples were prepared by rf-sputtering from a Si target partially covered by small erbium platelets in an Ar + H-2 + O-2 plasma. The maximum Er3+ luminescence occurs when 10 less than or equal to [O]/[Er] less than or equal to 40. Up to 3 O atoms form the Er coordination shell. The extra O increases the excitation of the Er3+ ions. When [O] increases and the density of states at mid-gap becomes larger than [Er], the Er3+ excitation rate decreases. In optimized samples the temperature quenching is less than a factor 2 from 15 to 300 K. The data allow us to conclude that: (a) Efficient room temperature Er3+ PL can be obtained from as-deposited a-SiOx:H(Er). (b) The role of O in a-SiOx:H(Er) is more than just providing non-centrosymmetric environments for Er3+. It also increases the Er3+ excitation rate. (C) 2000 Elsevier Science B.V. All rights reserved.