Gas source MBE growth of GaN-related novel semiconductors

This paper describes the results of gas source MBE growth of GaN-related novel semiconductors: GaN-rich GaNP ternary alloys and polycrystalline GaN. (1) GaN-rich GaNP alloys are successfully grown on sapphire substrates and show a large bandgap bowing, which means that the same bandgap energy can be obtained with small lattice-mismatch to GaN compared with InGaN. Phase-separation is also observed beyond a P composition of 0.015. However, by growing at lower temperatures the phase-separation is suppressed and the maximum P composition of 0.082 is obtained. The lowest bandgap energy obtained is 2.76 eV which is in the blue-violet wavelength region. (2) Polycrystalline GaN layers are grown on amorphous silica glass substrates. They show very strong photoluminescence. Both n-type and p-type conduction are achieved by impurity doping. The results suggest the possibility of the fabrication of large area, low cost photonic devices using polycrystalline GaN.