Abstract
Porous wide bandgap semiconductors have been widely studied in the last decade due to their unique properties compared to the bulk crystals. The high surface area, shift of bandgap, luminescence intensity enhancement and efficient photoresponse when porosity is formed can be tailored to fabricate new sensing devices. In this work, porous GaN was prepared by ultraviolet (UV) assisted electroless chemical etching method. The commercial Si doped n-type GaN film grown on two inches diameter sapphire (0001) substrate with GaN thickness of 5.5 μm was used in this study. The wafer was then cleaved into few pieces, and these samples were etched in HF:H2O2:CH3OH under UV illumination for 60 minutes. The structural properties was characterized using Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). Hydrogen sensor was subsequently fabricated by depositing Pt Schottky contact onto the porous GaN sample. The effect of sensing dilute H2 gas with different concentration which is 1% and 2% H2 in a N2 gas ambient was analyzed. The Schottky barrier height of the gas sensor samples was reduced upon exposure to gas. The porous GaN resulted better sensitivity compared to the as grown GaN sample in H2 gas sensing
Highlights
The fabrication of porous semiconductors has stimulated much research interest recently
Porous semiconductors show various important optical features compare to normal crystalline semiconductors such as higher intensity of photoluminescence emission, better photoresponce and shift of band gap [1].The research in porous GaN (PGaN) is strongly driven by the superior physical properties such as the excellent thermal, mechanical and chemical stability, as well as the potential shift of the bandgap [2]
The sample of porous shows a rapid increased in ∆øB compare to as grown GaN sample. This positive hydrogen concentration dependence can be attributed to the increased collision among hydrogen atoms that induced higher reaction rate and more hydrogen atom trapped at the semiconductor interface
Summary
The fabrication of porous semiconductors has stimulated much research interest recently. The dipole layer will be balanced by a modulation of the depletion layer, which leads to the change in the effective work function of the metal, changing the schottky barrier height and eventually change the electrical characteristics of the device [9,10]. This is a report to present gas sensing properties of Pd Schottky contact onto as grown GaN and porous GaN sample. Shah et al / Malaysian Journal of Fundamental & Applied Sciences Vol., No.1 (2012) 49-54
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