Time-resolved photoluminescence spectroscopy of Er-implanted porous silicon

Abstract

We have investigated the time evolution of the 1.54 μm Er 3+ photoluminescence (PL) intensity of Er-implanted porous silicon in the temperature range from 15 to 375 K. Er was implanted into porous silicon with a dose of 1 × 10 15 Er/cm 2 at 380 keV and annealed at 605 °C for 30 min. Upon optical excitation at 488 nm, erbium ions are excited by photo-generated carriers and an intense 1.54 μm PL is observed at room temperature. We have compared the time evolution of the 4I 13 2 → 4I 15 2 transition of Er 3+ to a double-exponential decay. The analysis suggests the existence of two classes of Er sites in porous silicon. This is supported by a study of the Er 3+ PL decay time as a function of excitation pulse width. The characteristic Er 3+ lifetimes in the two sites are 145 μs and 1.37 ms, respectively. In the temperature range from 15 to 150 K, the back transfer of energy from the excited erbium level 4I 13 2 to the host plays the dominant role in the thermal quenching of the Er 3+ luminescence. At temperatures above 150 K, the reduction in Er 3+ PL can mainly be ascribed to thermalization of bound electrons to the conduction band. We have compared the observed Er 3+ PL intensity with the result from a theoretical model and a good agreement is obtained.