Porous Quaternary Al_0.1In_0.1Ga_0.8N Film Formation via Photoelectrochemical Etching in HF:C₂H₅OH Electrolyte

Abstract

Pore formation in AlInGaN films using photoelectrochemical etching in different volume ratios of hydrofluoric acid:ethanol solution (1:1, 1:2, 1:3, and 1:4) has been investigated structurally, morphologically, and optically. A significant increase in root mean square roughness and photoluminescence intensity in AlInGaN film etched in 1:1 solution has yielded the highest pore density and the largest average pore size in the film. Moreover, the acquisition of the lowest total dislocation density as well as the largest in-plane biaxial stress relaxation in the film suggested potential use of the porous film as a template to grow subsequent layers for development of light-emitting diodes.

Facile and Large-Area Preparation of Porous Ag3PO4 Photoanodes for Enhanced Photoelectrochemical Water Oxidation

“…Besides the high photocurrent density, it is notable that the porous Ag 3 PO 4 photoanodes obtained with prolonged reaction times (≥20 h) also demonstrated better stability than nonporous ones, which could be known clearly from a 1 h successive PEC water splitting test carried out at 1 V vs Ag/AgCl (Figure b). The promotion in stability of the porous Ag 3 PO 4 photoanodes may be caused by the pores inside the Ag 3 PO 4 layer because the porous structures could help to release the stress at the near-surface region so that could help to keep them more stable than nonporous Ag 3 PO 4 according to previous studies. − SEM images of the 1-h and 20-h Ag 3 PO 4 photoanodes after experiencing the 1 h PEC water splitting tests, shown in Figure S11, clearly confirm that the continuous water oxidation reaction on the surface of the 1 h photoanode has caused a strong surface erosion of the originally nonporous Ag 3 PO 4 film (Figure S11a, b), leading to a non-negligible loss of active materials and decrease of the photocurrent density. However, the highly porous morphology of the 20 h Ag 3 PO 4 photoanode (Figure S11c, d), on the contrary, remained essentially the same after the 1-h stability test, ensuring the maintenance of the high photocurrent density.…”

Porous Formation in p-Type Gallium Nitride Films via 50 Hz Operated Alternating Current-Assisted Photo-Electrochemical Etching in Methanol-Sulfuric Acid Solution

“…where λ is X-ray radiation wavelength, n is diffraction order, d hkl is interplanar spacing, (hkl) is Miller's index, and θ is diffraction angle. 19 It was worth noting from Table I for the obtained FWHM as well as peak shift to lower angles for the porous films comparing to the non-porous film. The peak shift could be corroborated through the acquisition of larger lattice parameter c values in the porous films as compared to the non-porous film (inset of Figure 3).…”

“…Inexorably, a minute change in terms of peak width (peak broadening) and position shift was observed for the (0002)-oriented GaN diffraction peaks of porous films with respect to the non-porous film. This finding could be in association with the presence of microstrains in the films, which would cause changes in terms of full-width half maximum (FWHM) and lattice parameter c. Equations 1 and 2 have been used to determine the FWHM and lattice parameter c values 19 of the investigated films after taking into consideration of diffraction angle (θ 0002 ) obtained from rocking curve (RC) for symmetric (0002) ω-scan of the films.…”

Surface Alteration of Planar P-Type Gallium Nitride to Porous Structure Using 50 Hz Alternating Current-Assisted Photo-Electrochemical Etching Route

“…10 Massive studies on PEC etching of GaN have been particularly focused on either unintentionally or n-type doped GaN, [11][12][13][14] whereby similar focus has been also devoted to ternary In y Ga 1−y N, [15][16] as well as quaternary aluminum indium gallium nitride (Al x In y Ga 1−x−y N). 10,[17][18][19] Reason leading to preferred studies for both the unintentionally doped and n-type doped semiconductors was explained in term of physics for an upward band bending that happened at interface between the semiconductors and the etch solution. 20 Owing to the surface band bending to an upward position at the interface, a potential well for accumulation of photo-generated holes is created at the interface along with the movement of electrons away from the interface.…”

“…The movement of electrons and holes in opposite direction from and to the interface, respectively would bring impacts, straddling from electrochemistry aspect related to oxidative decomposition of GaN surface and cathodic reduction of the etch solution species, and extending to the science point of view regarding formation of vacancies or dislocations after the PEC etching, which would alter strain state in the GaN semiconductors. 19 Conversely, a divergence of PEC etching route was encountered for p-type doped GaN semiconductors, whereby the band is bent to a downward position at the interface rather than an upward position. 20 With this, surface of the p-type doped GaN will be lack of photogenerated holes that are required to perform the oxidative decomposition.…”