Integrated H2 nano-sensor array on GaN honeycomb nanonetwork fabricated by MEMS-based technology

Manipulation of nanostructures is difficult, making it tough to fabricate nano-device, let alone the fabrication of integrated nano-sensor. In this paper, a monolithically integrated H2 nano-sensor array on a GaN honeycomb nanonetwork (GaN-HN) are proposed and realized by combining GaN-HN MBE growth with standard silicon micromachining techniques. For each H2 nano-sensor unit, a H2 sensing element, a reference sensor, a micro-heater, a resistive temperature detector (RTD), and the current-circuit are integrated on a single chip. The H2 sensing element Pt/GaN-HN Schottky diode was well fabricated on the suspended GaN-HN with 20 nm out-of-plane deformation and 0.0016 mm−1 curvature. An Au/GaN-HN Schottky diode is proposed as the reference sensor and it is effective to reduce the output signal shift caused by ambient fluctuation to 20%. Moreover, the micro-heater on the free standing GaN-HN has high heating efficiency with fast heating and cooling time (2.3 ms and 2.5 ms, respectively). In addition, the performance of H2 nano-sensor unit at room temperature and at 75 °C heated by the integrated micro-heater with low power of 5.8 mW was recorded and discussed. At 75 °C, the response time τres and the recovery time τrec of the integrated H2 sensor are significantly shortened by a factor of 3.