The effect of hole confinement on photoluminescence from Er in SiGe/Si quantum wells

We have investigated the photoluminescence (PL) decay from Er implanted, or grown, into strained SiGe/Si multiple quantum well (MQW) structures grown by molecular beam epitaxy, and compared it with that of Er implanted into crystalline Si. The Er concentration in all MQW structures was of the order of 4 x 10(18) cm(-3). Prior to the erbium implant, PL originating from confined states in the strained MQWs confirmed that this was an optically active MQW sample. The implanted MQW sample was re-grown at 550 degrees C for 5 h and X-ray diffraction measurements after re-growth showed that a high degree of strain had been retained. The Er emission at 1.54 mu m was more intense from all MQW structures than from the implanted Si, but the PL decay time was not significantly different, suggesting that the excitation efficiency is improved when Er is in a quantum well structure and close to a long lived hole population, but the recombination efficiency is largely unaffected. When the excitation laser power density was increased by 10 times, the PL decay from the Er in the MQW structures was largely unaffected, but the PL decay time from Er in Si reduced; this is discussed in terms of non-radiative competition at end-of-range damage. It is proposed that the presence of a long-lived hole population increases the potential for efficient excitation of Er in the MQW structures. (C) 2007 Elsevier B.V. All rights reserved.