Lixia Zhao oral presentation (SN2-Tue3-2-6)
Etching Mechanism of Laterally Porous GaN and Its Optoelectronic Applications
Institute of Semiconductors, CAS, A35 Qinghua East Road, 100083 Beijing, China
Since the first report of porous silicon in 1990s, porous materials, in particular mesoporous materials, have been extensively investigated and widely used in various applications. Porous GaN have gain much attention since its excellent thermal, chemical and mechanical stability for the past two decades. Recently, a new type of porous GaN, laterally porous GaN has generated increasing interest and offered new opportunities to engineer and improve the performance of GaN-based optoelectronic devices. However, the etching mechanism and devices based on laterally porous GaN has still not been explored.
In our recent study, aligned porous arrays were fabricated in the GaN epilayer via a lateral anodic etching technique. The results show that anisotropic etching can occur at lower voltages, but it will gradually transform toward isotropic etching with increasing the voltage. Based on different structural and electrical analysis, the formation kinetics of porous GaN was investigated based on the etching current and the pore trajectories. It reveals that the two-stage characteristic of lateral etching，which is initially driven by the avalanche effect, then enter a steady state as a balance between the oxidation and dissolution of GaN at the pore tips.
With the porosification in GaN layer, a significant enhancement on the water splitting properties of GaN photoanode was obtained. In addition, the fabrication of GaN-based metal-semiconductor-metal (MSM) photodetectors based on this well-ordered laterally porous GaN shows a specific detectivity D* up to 5.3×1014 Jones under ultraviolet illumination. These findings and analysis show that this new type of lateral porous structure has a strong potential in optoelectronic applications.