Promising characteristics of GaN layers grown on amorphous silica substrates by gas-source MBE

Polycrystalline GaN layers are grown on amorphous fused silica glass substrates by gas-source MBE using ion removed electron cyclotron resonance (ECR) radical cell. Polycrystalline GaN grown here shows a strong photoluminescence without deep-level emission. The emission peak with a wide spectral half-width is red-shifted from the excitonic emission of a GaN layer grown on a sapphire substrate. The peak is excitonic from the excitation power and temperature dependencies of the PL spectrum. Photoluminescence excitation spectra show that the polycrystalline GaN has a large Stokes shift. The results suggest that the polycrystalline GaN has a large potential fluctuation due to a grain to grain potential distribution and that the strong emission originates from the lower-energy tail of the absorption spectrum. Such optical properties indicate that the polycrystalline GaN layers grown on the glass substrates are promising to fabricate large area and low cost light-emitting devices and solar cells. Polycrystalline optical device technology will be indispensable for industrial applications as well as the polycrystalline and the amorphous Si devices.