MOLECULAR-BEAM EPITAXY OF HIGH-QUALITY, NONSTOICHIOMETRIC MULTIPLE-QUANTUM WELLS

Multiple quantum wells (MQWs) have been grown at low substrate tempera tures by molecular beam epitaxy so as to incorporate excess arsenic. T his excess arsenic precipitates and preferentially coarsens to the low er band gap well regions with anneal. Despite the excess arsenic, thes e AlAs/GaAs MQW structures exhibit sharp excitonic features that are c omparable to those exhibited by stoichiometric MQW structures grown at standard temperatures. In addition to the sharp excitonic transitions , these MQWs possess ultrafast recombination lifetimes making them att ractive for photorefractive, electro-optic sampling, and saturable abs orption applications. (C) 1996 American Vacuum Society.