Electrochemical corrosion of III-nitride layers eventually proceeds during the long-term operation of lighting and ‘artificial photosynthesis’ III-nitride-based devices. Diversified chemical and morphological characterization of the anodic oxidation reaction of n-GaN may help precisely control it to prevent the devices from their degradation. In literature, this reaction is three-electron, but according to the analysis of reaction products in liquid and vapor phases, we found out that this process is six-electron. We ran series of n-GaN oxidation experiments in voltage range of 5 — 20 V in aqueous solutions of oxalic acid (pH = 1), sulfuric acid (pH = 0 – 4), sodium sulfate (pH = 7) and sodium hydroxide (pH = 10 – 13). The experiments were carried out in a two-electrode configuration with a Pt counter electrode in ambient conditions. According to the quantitative analysis of products of electrochemical oxidation of n-GaN, we propose its mechanism to involve the interaction of n-GaN with the solvent (solv) and to proceed as follows: 2GaN + 2n(solv) —&gt; N2 + 2[Ga(solv)n]ads3+ + 6e-, 2[Ga(solv)n]ads3+ —&gt; 2Ga3+ + 2n(oxidized solv) + 6e-. We ran cyclic voltammetry measurements in the three-electrode configuration using reference electrodes appropriate for the media investigated. Results on scanning electron and atomic force microscopic analysis of samples’ cross-sections and surfaces provide a solid basis for discussion of morphological development of the porosification process of anodic oxidation of n-GaN. The knowledge of chemical and morphological features of electrooxidation of n-GaN can clarify the ideas of designing and manufacturing III-nitride-based devices.

Electrochemical corrosion of III-nitride-based devices for artificial photosynthesis: Inevitable or useful?

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