Modelling the photoemission characteristics of parallel aligned (Al)GaN nanowall arrays assisted by built-in/external field

Abstract

The photoemission and electron collection properties of nanostructure photoemitter based on parallel aligned (Al)GaN nanowall arrays are investigated. In general, the photoelectric conversion efficiency of intrinsic GaN NWAs exhibit a significant improvement compared with planar photoemitter. Assisted by the built-in field induced by gradient decreasing Al component along axial direction of the nanowall, the proportion of emitting photoelectrons on each surface of a nanowall is redistributed and the collected photocurrent is obviously enhanced yet with a negative effect against quantum efficiency and emitted photocurrent. External field incorporation can tune the electron emitting path and improve the collection efficiency, but accompanied with a further decline in emitting photocurrent and quantum efficiency. For a certain configuration with nanowall height of 1 µm and spacing length of 1 µm, the optimum field intensity for emitting and collected photocurrent are respectively 0.3 and 0.5 V/µm. The alteration of photocurrent varied with field intensity dominated by the photoelectrons from the top surface and irradiated side face of the nanowall.