Formation of Porous GaAs by Pulsed Current Electrochemical Anodization: SEM, XRD, Raman, and Photoluminescence Studies

Abstract

Porous GaAs ͑-GaAs͒ has been fabricated using pulsed current electrochemical etching. Scanning electron microscopy ͑SEM͒ shows that the time off ͑T off ͒, time on ͑T on ͒, and cycle time ͑T͒ can promote thicker and more uniform -GaAs layers compared to those of direct current etching. Choosing suitable pulse parameters produces -GaAs layers with a thickness of 90 m and crystallite size of 2.4 nm. X-ray diffraction ͑XRD͒ shows a high degree of crystallinity of the samples. Photoluminescence ͑PL͒ spectra showed two or three PL bands besides the PL band of the single-crystalline GaAs ͑c-GaAs͒. Peak PL wavelengths were located approximately at 362, 426, and 540 nm.After the discovery of the room temperature visible photoluminescence ͑PL͒ in porous Si, 1 pore formation in III-V materials received a great deal of attention from the scientific community. Several approaches have been used to fabricate porous GaAs ͑-GaAs͒, including electrochemical anodization, spark processed porous, and laser-induced etching. 2-4 Most -GaAs reported to date have shown a certain degree of inhomogeneity with respect to morphology, surface chemistry, and PL. [5][6][7] showed that the porous layers formed in n + GaAs͑100͒ samples were uniform both laterally and vertically. The porous layers in the n-GaAs͑111͒ samples were relatively uniform, although their thickness fluctuated by as much as 20% on different parts of the wafer. Porous layers formed in n − GaAs͑100͒ were characterized by rectangular surface regions of 200 ϫ 300 m, where pores were initiated, while other parts of the surface remained unetched. Maosheng Hao et al. 8 have formed -GaAs using a two-step electrochemical anodization process, producing a high density of pores with uniform distribution in n-type GaAs. More recently, Mavi et al. 4 have fabricated GaAs nanostructure by laser-induced etching using Nd:yttrium aluminum garnet ͑ = 1.06 m͒ laser, producing nanostructure sizes controllable by changing laser parameters.Difficulty in controlling the nanoscale structure and related properties of GaAs remains as the main challenge. This obviously requires correlating the parameters of the synthesis process with the resulting nanostructure. The pulse current electrochemical approach, 9 if it attains sufficiently high controllability at the nanometer scale, seems to be a highly useful technique. In this technique, instead of using a dc current, a sequence of current pulses is used to form a porous material. Porous silicon with controlled thickness has been successfully prepared using this technique, which gives thicker and more uniform porous layers showing higher PL intensity. [10][11][12] The technique was also used to precisely control etching for processing nanodevices because the pulsed mode enables an extremely small etching rate of ϳ10 −5 nm per pulse. 13 In this work, we report on the formation of -GaAs by using the pulse current anodization technique. The main feature is the on/off cycle at fixed current density and electrolyte composition. The time when there is current, ...

Distinct UV–Visible Responsivity Enhancement of GaAs Photodetectors via Monolithic Integration of Antireflective Nanopillar Structure and UV Absorbing IGZO Layer

“…[36] Moreover, if etched GaAs surface is completely porous, a significantly broadened TO peak locating at 150-250 cm -1 should be identified. [37,38] However, the TO peak in Raman spectrum of GaAs nanopillar array remained sharp, indicating that the GaAs layer remained intact rather than being completely porous after MacEtch.…”

Effect of SiO₂ Nano-Interlayer to Characteristics of GaAs/Ge Heterostructure

“…XRD pattern from the GaAs/SiO 2 /Ge structure 图 GaAs/SiO 2 /Ge XRD 图 属砷空缺的光学声子模态，推断是室温溅镀成长 GaAs 时砷原子的位置被氧原子所占据，或是砷挥发而 产生砷的自生点缺陷所导致[11]。在照光的情形下，在 GaAs 的膜层中之砷的自生点缺陷会捕捉光生电子 SiO2 奈米绝缘层对 GaAs/Ge 异质结构特性之影响 Cross-sectional SEM image of the GaAs/SiO 2 (15min)/Ge heterostructure 图 2. GaAs/SiO 2 (15min)/Ge SEM 横截面图…”

Porosity-induced relaxation of strains in GaN layers studied by means of micro-indentation and optical spectroscopy

“…An attractive alternative is to enhance the development of other porous III-V semiconductor compounds, such as GaP, InP , and GaAs as well as the wide bandgap and corrosion resistant materials like GaN and SiC. [8][9][10][11][12][13] Wide bandgap III-nitride semiconductors are generally grown on sapphire or SiC substrates. The GaN, sapphire, and 6H À SiC semiconductors have in-plane lattice constants of 3.189 Å , 4.758 Å , and 3.08 Å , respectively, and have a thermal expansion coefficients of 5.59 Â 10 À6 /K, 7.5 Â 10…”