Terahertz emission from high stacking fault density m-GaN was observed using ultrafast pulse excitation. The terahertz signal exhibits a 360° periodicity with sample rotation and a polarity flip at 180°, characteristic of real carrier transport in an in-plane electric field parallel to the c axis induced by stacking fault -terminated internal polarization at wurtzite domain boundaries. The terahertz emission could be enhanced by several times relative to that from a stacking fault-free m-GaN sample, for which the terahertz signal emanated from surface surge currents and diffusion-driven carrier transport normal to the surface and was independent of the c-axis orientation.

Enhanced Terahertz Radiation from High Stacking Fault Density Nonpolar GaN. G.D.Metcalfe, H.Shen, M.Wraback, A.Hirai, F.Wu, J.S.Speck: Applied Physics Letters, 2008, 92[24], 241106