SELECTIVE EPITAXY OF GAAS/ALGAAS ON (111)B-SUBSTRATES BY MOCVD AND APPLICATIONS TO NANOMETER STRUCTURES

We demonstrate the selective epitaxy of GaAs/AlGaAs rectangular structures on SiO2 stripe-masked (111)B substrates by MOCVD. The structures have an exceedingly uniform and smooth (111)B top surface and {110} sidewalls. Furthermore, little lateral overgrowth is observed. No crystal growth occurs on the SiO2 mask region. The excellent thickness uniformity and absence of lateral overgrowth are accomplished by using a high growth temperature and a low AsH3 partial pressure. Using the resultant structure, we further demonstrate the lateral growth of n-AlGaAs/GaAs modulation-doped structures on the {110} sidewalls. This leads to the formation of lateral quantum wires. In these structures, there is no size fluctuation which is commonly present when dry etching processes are used. The mechanisms accounted for the desired growth conditions in both the vertical and the lateral direction are discussed.