No abstract

The feasibility of selective area growth of GaN by ammonia-MBE has been demonstrated on SiC substrates. Under typical growth conditions for ammonia-MBE, GaN was unable to nucleate on the bare SiC surface. However, GaN nucleation could occur instantly if the SiC surface was first seeded with a thin (300 A) AlN layer prepared by magnetron sputter epitaxy. Thus, GaN growth could occur selectively from a patterned, pre-deposited thin AlN seed layer, and effectively utilizing the exposed SiC surface as a pseudo mask. Evidence of lateral overgrowth was observed by scanning electron microscopy and X-ray diffraction studies. The selectively grown GaN patterns exhibited a strong tendency to form {10 1 11} or {10 1 12} type of facets with excellent smoothness.

No abstract

GaN/AlGaN quantum wells on GaN templates have been grown on (0001) sapphire substrates using the ammonia-molecular-beam epitaxy technique. The GaN template layers were of the type used previously for growing high-mobility, heterostructure field-effect transistor structures. The photoluminescence properties of the quantum wells showed strong quantum-confined Stark effect in good agreement with theoretical calculations, as well as evidence of carrier localization due to in-plane well width fluctuation. At low temperature, the quantum well emissions were dominated by two or more localized exciton levels. Carrier thermalization to the lower localized level was observed as the temperature was raised. Evidence of interwell transfer of photocarriers was observed, with the holes appearing to transfer in the direction of the internal field within the AlGaN barrier.