Fabrication of Double Heterostructure Aluminum Gallium Arsenide/Gallium Arsenide Lasers by Molecular Beam Epitaxy

摘要

Today there exists a need to be able to process increasing amounts of data at rates beyond the capabilities of existing purely electrical networks. To meet this need, networks which transmit data via an optical carrier rather than an electrical one are being developed. A necessary component of an optical network is a small, easily modulated source of coherent light. The only such source available is a laser diode. The first laser diode to operate continuously at room temperature was a double heterostructure (DH) (Al, Ga)As/GaAs laser prepared by liquid phase epitaxy (LPE). Much effort was subsequently devoted to reproducing those results by molecular beam epitaxy (MBE). MBE offers several advantages over LPE, such as control of composition and impurity profiles to atomic dimensions. Layers cna be grown on larger substrates and with a high degree of uniformity and reproducibility that is not possible with LPE. Despite these advantages, it was six years after the first continuous room temperature operation of an (Al, Ga)As/GaAs DH laser that a similar laser prepared by MBE was reported. The first MBE lasers typically had threshold current densities, Jth, about twice as large as similarly designed LPE lasers. Another three years passed before the art of MBE advanced to the point where it became possible to achieve laser performance equal to the LPE lasers. The presence of non-radiative recombination centers in the bulk (Al,Ga)As layers was shown to make a significant contribution to the high threshold current densities in MBE lasers.