Study Of GaN Electrostatic Comb Actuators On Patterned-SOI

Due to its advantages of miniaturization, monolithic integration and mass production, optical microelectromechanical system(MOEMS) is becoming a hot spot of research in the 21 st century. It is widely used in the fabrication of optical communication systems, optical display, optoelectronic devices, and other fields. Also, MOEMS greatly promotes the development of the communications, medicine, military and aerospace. As the most important part of MOEMS, the electrostatic comb drive could provide driving force and is widely researched. On the other hand, the third generation semiconductor material-gallium nitride has the advantages of wide direct bandgap and excellent light emitting property. It can work in hot, high-frequency and high-power condition. The growth of gallium nitride substrate is mainly conducted on sapphire, silicon carbide, silicon/SOI substrate. Furthermore, SOI could be machined compatibly with silicon micromachining technology and large-area gallium nitride thin film could be deposited on the SOI substrate. The integration of GaN and SOI to fabricate integrated new devices could be a promising research field.In this paper, gallium nitride micro electrostatic comb drive based on patterned SOI substrate is studied. The modeling and simulation of GaN/Si electrostatic actuator were carried out by the finite element software COMSOL. Analysis of the structural parameters influence on the performance of micro electrostatic comb drive is studied. The eigen frequency and vibration mode of the six lowest order modal of GaN/Si electrostatic actuator were analyzed and the modal of first and third were obtained.Based on the research of GaN-based silicon electrostatic drive, a GaN movabale grating based on SOI substrate was designed. The grating realizes orthogonal movement in horizontal and vertical direction by electrostatic comb drive. The grating is studied with the theory of guided mode resonance, and the simulated resonance peak is 25.742 μ m. The horizontal and vertical displacement and the modal analysis were conducted by the use of COMSOL software. Based on the simulation results, the designed device was processed by the MBE growth of GaN on the patterned SOI substrate.Finally, the values of drive displacement were obtained in the experiments. There is some deviation between the tested horizontal displacement values and the simulated theoretical values. The vertical displacement has a well linear relation with the square of the applied voltage. The photoluminescence spectra of the multiple quantum well of GaN membrane was investigated by laser Raman spectrometer and FE-SEM was used to observe the morphology of the device.