GaPAsSb type-I quantum wells and symmetric InGaAs/GaPAsSb/InGaAs type-II qu
antum wells are proposed as long wavelength active layers for GaAs based op
toelectronic devices. Room temperature photoluminescence from 1.3 to 1.5 mu
m is observed from the type-II quantum wells, while low temperature photol
uminescence at 1.25 mu m is observed from type-I quantum wells. A reflectio
n high-energy electron diffraction peak that is extended pal-allel to the s
urface, while its width is perpendicular to the surface is narrow, suggests
that spontaneous lateral composition modulation occurs in the GaPAsSb laye
rs. (C) 2000 American Vacuum Society. [S0734-211X(00)02703-7].