Epitaxial Growth and Selectivity of AIxGal-xAs Using Novel Metalorganic Precursors

Diethyl aluminum chloride and diethyl gallium chloride were successfully employed as precursors for the epitaxial growth of AI=Ga ~ =As. The composition, thickness, and compositional uniformity of these layers were strong functions of the growth temperature, as determined with double-crystal x-ray diffraction and photoluminescence m asurements. A thermodynamic model based on the free energy minimization of the expected gas and solid phase constituents is pre-sented to explain these trends and other growth chemistry effects. Selective pitaxy was also investigated. AlxGal_=As was selectively grown on GaAs wafers masked with S iQ or SigN4 under certain conditions. In contrast, AlAs growth was not selective. Selectivity of Al~Gal_xAs improved with increasing diethyI gallium chloride mole fraction and with increas-ing temperature, in accordance with thermodynamic considerations. Thermodynamic analysis of this growth chemistry indicates that various multinary semiconductors can be grown selectively using related metalorganic-chloride precursors. The AlxGal-xAs/GaAs ystem is technologically impor-tant for applications in double heterostructure lasers (1, 2), photodetectors (3), and heterojunction field effect transis-tors (4, 5). The versatility of AI=Gal_=As emanates from the rapid increase in the bandgap with increasing A1 mol