Impurity-induced layer disordering of quantum-wellheterostructures: discovery and prospects

摘要

The circumstances leading to the discovery in 1980 ofnimpurity-induced layer disordering (IILD) of AlAs-GaAs (AlxGan1-xAs) quantum-well heterostructures (QWHs) and superlatticesn(SLs) are described. In view of the great stability of a QWH or SLn(AlAs-GaAs) against ordinary thermal annealing, IILD came as a surprise,ni.e., the lower temperature (selective) change from red-gap QW crystalnto yellow-gap bulk crystal. Layer disordering can be carried out mostneffectively, via diffusion or implantation, with two-site dopants suchnas Zn (acceptor) or Si (donor), but is not restricted to activenimpurities alone. This maskable planar technology, which (with crystalnconservation) transforms a coarser layered III-V “alloy” tona smoother stochastic alloy, and higher bandgap, is capable of forming,nas desired, regions that confine carriers and photons. Accordingly, IILDnhas broad and growing use in optoelectronics (lasers, waveguides, etc.),nparticularly for III-V systems employing Al and Ga which easilynsubstitute for one another and are sensitive to IILD. The atomicnrearrangement of diffusion, a small scale (microscopic) lattice change,nis in essence “amplified” by IILD into a large scalen(macroscopic) layer change (patterned) that provides a method to studynIII-V diffusion mechanisms. IILD, a planar technology and growing areanof work, is useful in optoelectronics applications as well as for basicndiffusion studies in III-Vs and potentially other crystal systems