A photovoltaic pn junction micro vertical comb-drive actuator

This study reports a novel micro electrostatic vertical comb-drive actuator (VCA) driven by the photovoltaic effect that results from incident light. The vertical comb electrodes have a pn junction structure (named pn-combs). The VCA with pn-combs can be driven by the photovoltaic effect. The combination of the photovoltaic effect and reverse bias can further increase the driving amplitude of the VCA. To demonstrate the feasibility of the proposed concept, the VCA with pn-combs was fabricated on an epitaxial silicon wafer (epi-wafer) and successfully driven resonantly by intensity-modulated laser light. The first torsional mode of a typical fabricated VCA is at 1.46 kHz. Moreover, VCA driven using (1) optical driving, and (2) optical driving with dc reverse bias, were also demonstrated. The angular displacement of the VCA was ±3.8 m deg by optical driving. The angular displacement of the VCA significantly increased to ±41 m deg after applying an additional dc reverse bias of 5 V.