GaN‐based Schottky diodes for hydrogen sensing in transformer oil

Abstract

We report the demonstration of robust, GaN-based hydrogen sensors for use directly in transformer oil. These 1 mm 2 Schottky diodes were immersed in a closed loop with Voltesso insulating oil for 21 months of continuous testing. They showed good reproducibility in response to hydrogen gases, while exposed to varying temperatures. We will briefly discuss the transformer monitoring application, the device design and fabrication process, and the sensor performance from 21-months of testing. Transfer functions from oil temperature and dissolved gas concentration have been quantified, and those will be briefly discussed. These new sensors offer a novel alternative to electrochemical cell-based sensors for various applications.

Low-resistance Ni-based Schottky diodes on freestanding n-GaN

“…3,4 GaN layers grown on insulating sapphire substrates have a relatively high defect density which can be expected to compromise the ideality and reverse leakage current in Schottky diodes. 5,6 While the leakage current can be reduced by surface treatments, 7,8 the large reduction in the electron mobility for carrier transport in the lateral direction compared with vertical transport, 9 means that the resistance of such diodes can be large.…”

Review of Dissolved CO and H2 Measurement Methods for Syngas Fermentation

“…Measurements of DH concentration in transformer oil were reported with different work function type sensors [ 234 , 236 , 237 ] and optical fiber sensors with fiber Bragg gratings (FBGs) [ 233 ]. Due to good insulation of transformer oil, the work function type DH sensors measure the voltage shift generated from the dipole layer at the metal (usually palladium)-semiconductor interface [ 236 , 237 ] or the conductivity change from interactions between H 2 and palladium nanowires [ 234 ]. Optical fiber DH sensors exploit the H 2 absorption property of palladium metal at room temperature to generate a mechanical strain, which can be measured through a wavelength change of transmitted light [ 233 ].…”

Trace Detection of Dissolved Hydrogen Gas in Oil Using a Palladium Nanowire Array

“…Until recently, DGA has involved the off-line measurement of gases in aliquots of oil using gas chromatography. ,,, This process is time-consuming, expensive, and prone to sampling error caused by temporal and spatial fluctuations in dissolved gases within the enormous oil volume of the transformer. These considerations have motivated the development of oil-immersed gas sensors that are capable of the continuous, real-time monitoring of dissolved gases (see Table ). ,,− A unique set of analytical challenges exists for these sensors. In the case of dissolved H 2 , a limit-of-detection well below 100 ppm is required, the dynamic range of the sensor should extend to at least 1000 ppm, and the sensor should not be damaged by exposure to higher H 2 concentrations .…”