1.54 μm photoluminescence of in situ erbium-oxygen co-doped silicon films grown by ion-beam epitaxy

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Abstract
Erbium‐doped silicon films are grown by ion‐beam epitaxy using an electric‐mirror sputtering‐type metal ion source in an ultrahigh vacuum. In situ erbium doping with concentrations ranging from 1×1016 to 6×1020 cm−3 is achieved by sputtering the erbium metal pellet with ions extracted from the silicon metal ion source. The oxygen concentration in the films, which is closely related to the effective luminescence of erbium in silicon, is also controlled in situ over the range from below 1×1018 to 2×1020 cm−3 by using argon gases containing 1 ppb–100 ppm of oxygen impurities. The erbium incorporation efficiency drastically increases (by two or more orders of magnitude) when oxygen is contained in the argon gas during film growth. Erbium segregation is well suppressed by the oxidation. Photoluminescence with a wavelength of 1.54 μm is clearly observed in as‐deposited films grown typically at 500 °C with argon gas containing 5 ppm of oxygen. The maximum luminescence intensity is obtained at an erbium concentration of about 2×1018, above which the intensity drastically decreases. This decrease is probably caused by degradation of the crystallinity of host silicon film or the formation of erbium precipitation.