GaAs/Ge/GaAs heterostructures by molecular beam epitaxy

We report high quality GaAs/Ge/GaAs heterojunctions grown by molecular-beam epitaxy. Antiphase domain (APD) free GaAs on Ge growth, as verified by high-energy electron diffraction and transmission electron microscopy, has been achieved for epitaxial (100) Ge surfaces misoriented towards [011] while APDs are observed to annihilate after roughly 500 Å of GaAs growth on nominally (100) epitaxial Ge. The outdiffusion of Ga and As into epitaxial Ge and outdiffusion of Ge into epitaxial GaAs was investigated by in situ x-ray photoemission spectroscopy and secondary ion mass spectroscopy. The electrical properties of the heterojunctions are studied and the transistor characteristics of a prototype N–Al0.22Ga0.78As/p+-Ge/n-GaAs heterojunction bipolar transistor is presented.