Abstract
GaN and NiO/GaN electrodes were characterized by impedance spectroscopy measurements in 0.1 M NaOH. We observed the suppression of the surface states capacitance due to the modification of the chemical state of superficial Ga atoms by NiO. This result suggests that the carriers involved in the photocorrosion of GaN in alkaline conditions originate in its surface states. In addition, we characterized the epitaxial relationship between the NiO particles deposited on GaN by transmission electron microscopy, finding the NiO{111}||GaN{0002} and NiO[220] ||GaN[112¯0] symmetry constraints.
Highlights
III-nitrides are of great interest in technological applications due to their optoelectronic properties
They are widely used in light-emitting diodes (LEDs) [1,2] and lately in microLEDs [3,4] because of the possibility of tuning their emission wavelength based on the metallic stoichiometry of their active region
Their origin in Ga-polar GaN has been attributed either to dangling bonds of Ga atoms at the surface or to Ga adatoms bonded to three surface Ga atoms [14,15]. These states are responsible for the GaN Fermi level pinning by taking carriers from the space-charge region (SCR) near the GaN surface [16]. These states can trap the electrons generated in the SCR, which is detrimental for photocatalysts, an oxidation treatment seems to passivate them partially [17]
Summary
III-nitrides are of great interest in technological applications due to their optoelectronic properties. They are widely used in light-emitting diodes (LEDs) [1,2] and lately in microLEDs [3,4] because of the possibility of tuning their emission wavelength based on the metallic stoichiometry of their active region They have adequate band edges positions to drive water splitting [5] and artificial photosynthesis reactions [6,7,8,9,10,11], which is one of the most stringent requirements for photocatalysts of those reactions. Their origin in Ga-polar GaN has been attributed either to dangling bonds of Ga atoms at the surface or to Ga adatoms bonded to three surface Ga atoms [14,15] These states are responsible for the GaN Fermi level pinning by taking carriers from the space-charge region (SCR) near the GaN surface [16]. These states can trap the electrons generated in the SCR, which is detrimental for photocatalysts, an oxidation treatment seems to passivate them partially [17]
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