Haynes-Shockley experiment analogs in surface and optoelectronics: Tunable surface electric field extracting nearly all photocarriers | Science Advances

Photocarriers predominantly recombine at semiconductor surfaces and interfaces, assuming high bulk carrier lifetime. Consequently, understanding the extraction of photocarriers via surfaces is critical to optoelectronics. Here, we propose Haynes-Shockley experiment analogs to investigate photocarrier surface extraction. A Schottky junction is used to tune the silicon near-surface electric field strength that varies over several orders of magnitude and simultaneously observe variations in broadband photocarrier extraction. Schottky barrier height and surface potential are both modulated. Work function tunable indium tin oxide (ITO) is developed to precisely regulate the barrier height and collect photocarriers at 0 V bias, thus avoiding the photocurrent gain effect. All experiments demonstrate >98% broadband internal quantum efficiency. The experiments are further extended to wave interference photonic crystals and random pyramids, paving a way to estimate the photogeneration rate of diverse surface light-trapping topologies by collecting nearly all photocarriers. The insights reported here provide a systematic experimental basis to investigate interfacial effects on photocarrier spatial generation and collection.