THE GROWTH AND PROPERTIES OF MIXED GROUP-V NITRIDES

Bearing in mind the problems of finding a lattice-matched substrate fo r the grow-th of binary group III nitride films and the detrimental ef fect of the large activation energy associated with acceptors in GaN, we propose the study of the alloy system AlGaAsN. We predict that it m ay be possible to obtain a direct gap alloy, with a band gap as wide a s 2.8eV, which is lattice-matched to silicon substrates. The paper rep orts our attempts to grow GaAsN alloy films by molecular beam epitaxy on either GaAs or GaP substrates, using a radio frequency plasma sourc e to supply active nitrogen. Auger electron spectra demonstrate that i t is possible to incorporate several tens of percent of nitrogen into GaAs films, though x-ray diffraction measurements show that such films contain mixed binary phases rather than true alloys. An interesting o bservation concerns the fact that it is possible to control the crysta l structure of GaN films by the application of an As flux during growt h. In films grown at 620 degrees C a high As flux tends to increase th e proportion of cubic GaN while also resulting in the incorporation of GaAs. Films grown at 700 degrees C show no evidence for GaAs incorpor ation; at this temperature, it is possible to grow either purely cubic or purely hexagonal GaN depending on the presence or absence of the A s beam.