ELECTRICAL TRANSPORT AND GAS SENSING OF GaN AND ITS HETEROSTRUCTURES
To monitor inflammable, harmful and toxic gases there is a need for highly efficient and sensitive gas sensors. In this project, temperature dependent CO gas sensing the properties of polar and non-polar GaN, Nanoflower decorated GaN and AlGaN films grown by plasma assisted molecular beam epitaxy and commercially purchased GaN template grown by metal organic vapour phase epitaxy have been explored. All the devices have (Metal semiconductor Metal) MSM geometry, with contacts made up of gold and active surface area of 0.04 cm2 each. The non-polar GaN device shows the highest sensitivity among all devices. Further the room temperature Photoluminescence spectroscopy and Raman spectroscopy of these samples are analysed to obtain the bandgap, defect energy states and stress in the film respectively. The determination of the primary current conduction mechanism and barrier height in a Schottky barrier diode device is an important factor as it directly relates to the turn-on voltage and reverse leakage current in our device. To investigate the leakage current, conduction mechanism, temperature dependent barrier height and ideality factor temperature dependent current voltage measurements are taken in vacuum for the ZnO/GaN and WSe2/GaN heterostructures. The barrier height of all the MSM devices are found increase with increase in temperature. The primary conduction mechanism in the Polar GaN sample is found to be Pool-Frenkel attributing for higher currents in the MSM device.
Keywords: Metal semiconductor Metal, Schottky barrier height, Current voltage, Electrical Transport, Gas Sensing, Nanoflower Decorated GaN & AlGaN