Characteristics of porous GaN prepared by KOH photoelectrochemical etching

Abstract

This paper presents the structural and optical studies of porous GaN prepared by photoelectrochemical etching in diluted KOH under different etching durations. Such etching technique is a cheaper and simpler way of fabricating porous structure. The as-grown and porous GaN samples were investigated by field emission scanning electron microscopy, high resolution X-ray diffraction and Raman spectroscopy. Field emission scanning electron microscopy measurement allowed us to observe the morphology of the porous samples, and we found that the pore density increased with etching duration. From high resolution X-ray diffraction characterisation, the width at half maximum value of the rocking curve at (0002) and (10 12) plane decrease for all porous samples because of the reduction in dislocation density. Furthermore, as compared to the as-grown sample, the porous samples exhibit a significant enhancement of Raman peak intensity because of multiple scattering of light from the GaN crystallite sidewalls. Overall, this study shows that the surface nanostructure could improve the structural and optical properties of GaN. This is an initial demonstration to show the prospect of the porous GaN structure in optical and sensor applications.

Effect of KOH Concentration on the Properties of Undoped Porous GaN on Sapphire Substrate Prepared by UV assisted Electrochemical Etching

“…Thus, the obtained results show that porous structure might enhance the optical properties of GaN and could be promising material for optical device applications. This trend is also in general agreement with other researchers [1,3,21] and consistent with the results obtained from FESEM and HRXRD measurements as previously discussed.…”

“…From Table 1, it can be seen that the value of dislocation density are decreased as the KOH concentration increased relative to as-grown GaN sample. Similar findings are also reported by several groups [21,27]. The results are in similar covenant with the FESEM measurements as defective region at the grain boundaries are highly etched at higher KOH concentration.…”

Porous nitride semiconductors reviewed

“…This suggests that porosity must be on the template surface in order to provide strain relief for the regrown layer. As well as strain relief, reduction of the FWHM of XRD rocking curves has been used to suggest that films grown on porous templates have lower dislocation density [49,67] and this has also been shown in AlGaN grown on porous and non-porous GaN templates shown by AFM measurements after acid treatment to expose dislocations [56]. It has been suggested that part of this comes from the annihilation of threading defects at voids forming in the porous layer during regrowth [117].…”

“…Secondly, it must be able to prevent the formation of solid oxides forming and passivating the surface. In forming porous silicon by anodization, this requires HF based electrolytes, in order to dissolve SiO 2 [20], but a wide variety of electrolytes have been used to create porous nitride structures via ECE or PECE including both acids, such as sulphuric acid [29], HF [31] and oxalic acid [48] as well as bases, such as NaOH [32] and KOH [49]. The pH of the electrolyte has been suggested to influence the resulting pore morphology in PECE due to the relative negative charge of some dislocation centres [50].…”

Electrochemical Sensor Made with 3D Micro-/Mesoporous Structures of CoNi-N/GaN for Noninvasive Detection of Glucose

“…As for the GaN material (the third-generation semiconductor), it has advantages such as (1) good electroconductibility and stability, − and (2) being capable of precise control of the composition and morphology at the atomic level using industrial technology, such as metal–organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) growth . Thus, the GaN material with a three-dimensional (3D) open structure is promising for CC, but anodic corrosion of GaN materials in an electrolyte still needs to be solved. − …”