Bias-dependent Photoabsorption Properties of GaN Porous Structures under Back-side Illumination

摘要

Photoabsorption properties of GaN porous structures were investigated by measuring photocurrent and light transmittance under monochromatic light with various wavelengths. The measured photocurrents on the porous GaN electrode were larger than those on the planar electrodes, and those were observed even under illumination with lower photon energy than the bandgap energy of bulk GaN. Moreover, the light transmittance that was measured in the back-side illumination (BSI) mode depended strongly on the applied voltage to the porous electrode with change of the photocurrents. The observed photoabsorption properties can be qualitatively explained by the Franz-Keldysh effect; namely, the high electric field induced in the GaN porous structure easily causes a redshift of the photoabsorption edge.