ABSTRACT
The key issue in designing DHBT structures is how to suppress the current blocking action caused at the collector heterojunction. Several techniques, such as an InGaAs/InGaAsP/InP composite layer [1], InGaAs/InAlAs chirped superlattice [2,3], InAlGaAs grade [4,5], and GaAsSb/InP abrupt type II heterojunction [6,7], have been proposed. Here, we used an InGaAs/InGaAsP/InP step-graded collector, which was grown by metalorganic vapour phase epitaxy (MOVPE) on a 3-inch substrate. We employed carbon for base dopant to achieve the abrupt as-designed doping profile.
