Photoluminescence properties of strained molecular-beam epitaxy Si1 12xGex/Si multiquantum wells

Si1 12xGex/Si multiquantum well (MQW) structures grown by molecular-beam epitaxy exhibit a broad, intense photoluminescence (PL) peak 3c120 meV below the band gap energy and/or phonon-resolved, near-band gap PL, depending on the MQW strain and the growth conditions.The origins of these two PL types have been identified. For MQWs with thin alloy layers ( 6440\u2013100 \uc5), the SiGe PL at 2 K is dominated by boron bound\u2013exciton annihilation, which yields phonon-resolved transitions. For thicker layers, the PL is dominated by a broad, intense peak due to exciton recombination at small ( 64 3c15 \uc5) interstitial-type platelets that occur in densities up to 3c109 cm 122/QW. Etching experiments revealed that within a given MQW the platelet density is lowest in the first grown well and progressively increases in subsequent wells with increasing strain energy density, indicating that platelet formation is strictly a morphological phenomenon.NRC publication: Ye