Disordered superlattices

Disordered superlattice (d-SL) is a kind of disordered crystalline semiconductors in which atomic alignment is disordered in some directions, but ordered in other directions. The d-SL exhibits remarkable luminescence capability caused by artificial disordering along a one direction. The (AlGaAs)(AlGaAs), (AlP)(AlGaP), and (SiGe)Si d-SLs are grown. The temperature dependence of (AlGaAs)(AlGaAs) photoluminescence (PL) is described. The disordered effect appears most strongly in the (AlAs)(GaAs) d-SL. The (AlP)(GaP) d-SL emits electroluminescence 4.5 times stronger than the bulk alloy and the ordered superlattice. The PL peak wavelength of the (AlP)(AlGaP) d-SL becomes shorter than that of the (AlP)(GaP) d-SL, because the AlGaP superlattice band structure is a type II. The (SiGe)Si d-SL also emits enhanced luminescence. For further improvement, the increases in the band offset and in the total number of monolayer in the superlattice are required. The physical mechanism for unusual luminescence properties of a d-SL is discussed in terms of carrier localization and confinement. A disordered superlattice is suggested to be a promising material for the enhancement of the luminescence capability.