Impurity-induced disordering in AlGaInP superlattices studied using cross-sectional scanning tunneling microscopy

摘要

The effect of doping an (Al0.3Ga0.7)(0.5)In0.5P/Al0.5In0.5P superlattice was investigated using cross-sectional scanning tunneling microscopy (XSTM). Two superlattices of different doping concentration were studied; namely, a superlattice where both well and barriers were doped, and a superlattice with only the barriers doped. Interdiffusion and impurity-induced layer disordering at the well and barrier interfaces is reported for both superlattice structures. However, the extent of interdiffusion across the interfaces, when only the barrier was doped, was measured to be at least 2.5 times more than the superlattice with both well and barriers doped. The considerable extent of Al-Ga interdiffusion in the barrier doped superlattice is thought to be caused by Zn diffusion at the (AlxGa1-x)(0.5)In0.5P heterostructures during Zn activation at 690 degreesC. This activation process encourages the segregation of the acceptor Zn out from the AlInP barrier layers and into AlGaInP well layers. In addition, this process is also known to enhance Al and Ga diffusion rates. XSTM images also show alloy clustering at both differently doped superlattices. Interdiffusion, alloy clustering, and interface roughness observed at the AlGaInP superlattices would have a detrimental effect on the suitability of a multiquantum barrier structure, based on this material system, to improve quantum confinement in red laser devices. (C) 2004 American Vacuum Society.