Micromachined piezoelectric microphone with high signal to noise ratio

This study reports a novel electrostatic vertical comb-drive micro-actuator (VCA) driven by the photovoltaic effect that results from the incident light. The vertical comb electrodes are composed of pn-junction structures (named PN-combs). The VCA with PN-combs can be driven by the photovoltaic effect and/or reverse electrical bias. The VCA with PN-combs was fabricated on an epitaxial silicon wafer and successfully driven by intensity-modulated laser light and reverse bias. The combination of the photovoltaic effect and reverse bias can further increase the mechanical scan angle of the VCA. Experiments demonstrate the feasibility of four driving methods, including optical driving, optical driving with DC reverse bias, electrical driving and electrical driving with DC photovoltaic voltage.