A GaN-based two-sensor array for methane detection in an ethanol environment

We demonstrate that photoelectrochemical (PEC) etching of GaN layers in KOH or H3PO4 solutions leads to the formation of specific surface morphologies which cause the material to exhibit different sensitivities to certain gases. PEC etching in a KOH solution results in a pyramidal morphology of the layer which exhibits a high sensitivity to methane gas, whereas etching in a H3PO4-based solution leads to the formation of individual nanoneedles with a high sensitivity to alcohol vapours. We also investigated the gas sensitivity of GaN structures with different morphologies as a function of temperature and the cross sensitivity to humidity. These results culminated in an integrated two-sensor array for methane detection in environments containing ethanol vapours. A new method of improving the recovery time characteristics of the sensor by applying high-voltage pulses is proposed.