화학공학소재연구정보센터
Thin Solid Films, Vol.306, No.2, 346-351, 1997
Growth and properties of nonperiodic multiple thin films
Nonperiodic multiple thin films of AlGaAs and SiGe materials are grown by molecular beam epitaxy, and their luminescence properties are investigated. The layer thicknesses of individual films are nonperiodically, i.e., randomly varied along the growth direction. The multiple thin films become superlattices with the layer thicknesses varied randomly. They can be called disordered superlattices (d-SL) in contrast with a conventional, ordered superlattice (o-SL). The luminescence capability is remarkably enhanced by nonperiodic thicknesses. The photoluminescence (PL) intensities of AlAs/GaAs and Si/Ge d-SLs are observed to be greater at least 500 times at 77 K and about 10 times at 10 K, respectively. The PL decays slow down with increasing temperature as compared with that of an o-SL. The physical mechanism for the unusual luminescence capability can be interpreted in terms of carrier localization caused by the nonperiodicity. Nonperiodic multiple thin films or d-SL can be considered as a promising material for the enhancement of the luminescence capability.