Strain relaxation and dislocation filtering in metamorphic HBT and HEMT structures grown on GaAs substrates by MBE
The production of InP-based epiwafers on GaAs substrates by molecular beam epitaxy is achieved through the use of metamorphic buffers (M-buffers) consisting of graded InAlAs or bulk InP layers. Each M-buffer demonstrates a unique surface morphology and strain relaxation mechanism, as demonstrated by AFM, SEM, and TEM. HEMTs and HBTs were grown on GaAs substrates using the two M-buffers, and their transport properties and dc parameters were compared with baseline structures grown on InP substrates. The structures grown with the InAlAs M-buffer were much closer to the baseline than those grown using the InP M-buffer. Incomplete dislocation filtering in the InP M-buffer may be the source of this degradation.