Optical doping of silicon with erbium by ion implantation

Abstract

New procedures to incorporate high concentrations of erbium in silicon are presented, together with measurements of the characteristic photoluminiscence at 1.5 μm of Er 3+ in silicon. Er-doped amorphous Si was prepared by implantation of 5.4×10 15 Er/cm 2 at 250 keV into 550 nm thick amorphous Si surface layers prepared by Si implantation. The incorporation of Er in crystalline Si was investigated for Si(100) implanted with 250 keV Er at 9×10 14 cm −2. The amorphized Si layers were crystallized by either thermal solid phase epitaxy (SPE) at 600°C, or ion beam induced epitaxial crystallization (IBIEC) at 250°C. Segregation of Er is observed during SPE, with Er concentrations up to 10 20 cm −3 remaining trapped in the crystal ( X min ≈ 5%) after regrowth. Under IBIEC, the original Er profile is completely trapped in the crystal ( X min ≈ 10%). Thermal annealing was used to optically activate the Er. After annealing at 400°C, the Er-doped amorphous Si layers show a very small photoluminescence intensity (at 77 K) around 1.5 μm, superimposed on a defect band from the amorphous Si itself. For samples crystallized by SPE or IBIEC the maximum photoluminescence signal (at 77 K) is obtained after annealing at 1000°C. The intensities are much higher than for Er in amorphous Si. SPE regrown samples show sharp spectra peaked at 1.54 μm, while IBIEC samples exhibit a broad spectrum, ≈ 0.1 μm wide, peaked at 152 μm. The similarities and differences in optical spectra for the different Er-doped materials are discussed.