Photo-absorption and electron collection of field-assisted GaN nanohole array photocathode

Abstract The light absorption and photo-generation rate under different periods, filling factors (FF), hole depth and inclination angles are studied. The NHA exhibits a larger light absorption compared with the planar film, which is about 99.99973%. Based on the three-dimensional continuity equation, the quantum efficiency (QE) and collection efficiency (CE) of the field-assisted GaN NHA and the graded compositional AlGaN NHA are calculated. The QE and CE of the GaN NHA with a period of 200 nm, a filling factor of 0.05, an inclined angle of 10°, and a field intensity of 2 V/µm are 62.7% and 62.6%, respectively. In addition, the graded compositional AlGaN structure has a more improved effect on the vertical NHA. Compared with the uniform GaN NHA, the electron collection of AlGaN NHA ratio is increased by 2.4 times. The design principles proposed in this work provide guidance to reasonable parameters for the application of NHA photocathodes.