Preparation of nanoporous GaAs substrates for epitaxial growth

physica status solidi (c), 2012

Comptes Rendus Chimie, 2013

2012

Oriented pore networks in GaAs substrates were created by electrochemical dissolution. Pore etching duration in the range of 0.5 to 450 s was used. The porous substrates were treated for 16 – 24 hours at 250 – 350 ° C in high vacuum and ultra pure hydrogen. Low supersaturation overgrowth of the porous substrates by InxGa1-xAs (x<4%) was realized by Liquid Phase Epitaxy (LPE). Shorter pore etching time resulted in better epitaxial layer morphology. The influence of the melt supersaturation on the properties of the overgrown strained layer is discussed in detail. The maximum In content at which the layer shows good quality was increased from 2.8% for a conventional substrate to 3.4% on a porous substrate.

American Journal of Applied Sciences, 2008

GaAs thin film has been grown on porous silicon by metal organic chemical vapour deposition (MOCVD) for different growth temperatures using atomic layer epitaxy (ALE) technique. The morphology of GaAs layer was investigated by atomic force microscopy (AFM). The effect of growth temperature is studied using photoluminescence measurements (PL).The photoluminescence spectra revealed a dissymmetry form toward high energies attributed to strain effect resulting from the lattice mismatch between GaAs and porous Si substrate.

Electrochimica Acta, 2011

The electrochemical etching behaviors of GaAs on smooth and textured surfaces were systematically investigated in aqueous KOH electrolytes. When the applied potential was higher than the pore formation potential (PFP), the electrochemical etching of the smooth surface could be categorized into three regions: pore/wire formation, texturing, and electropolishing regions. Triangular GaAs nanowires were observed at low potentials while pronounced lateral etching occurred at high potentials. In the case of the textured surface, which consisted of groove arrays, more complicated etching behavior was demonstrated. The pore growth direction changed from 1 1 1 B to 0 0 1 at a high current density while accompanying a drastic change in the pore morphologies such as tetrahedron-like pores along 1 1 1 B transforming into 200 m deep pores propagated along the 0 0 1 direction.

Semiconductor epitaxial growth has progressed to pseudomorphic, lattice mismatched systems where a small amount of strain is accommodated in very thin layers. We investigate the concept of epitaxial growth on porous substrates, which can lead to the increased critical layer thickness and reduction of the density of threading dislocations. Both crystalographically oriented and current line oriented pore networks in InP and GaAs were created by electrochemical dissolution. Heat treatment of InP pores at 650 ºC and GaAs pores at 700-850ºC converted them into microcavities The capability of improved structural quality homo-and heteroepitaxially overgrown films is demonstrated on InAs and GaInAs layers with a different composition grown on porous GaAs substrates. Another important application of porous semiconductors is related to the preparation of nanocomposite structures.

Journal of Nanotechnology & Advanced Materials, 2014

Porous GaAs was prepared using electrochemical anodization technique of a cristalline GaAs wafer in hydrofluoridric (HF) acid based-solution at different manufacturing conditions. The physical properties of porous GaAs are mainly determined by the shape, diameter of pores, porosity, and the thickness of deposited porous layers. Depending on the etching parameters such as current density, HF concentration or substrate doping type and level, the physical properties of porous GaAs can be varied. In the present work, we investigate the structural and optical properties of porous GaAs etched at different current densities. The PL spectra of the porous layers reveal the presence of infrared and visible peaks observed at 1.42 and 1.80 eV respectively. The infrared PL peak is associated with the band gap edge of bulk GaAs and the visible PL band is due to quantum confined transitions in GaAs crystallites, induced by electrochemical etching. Both peak wavelengths and intensities of PL peaks vary as versus the treatment of samples. The refractive index and the extinction coefficient of the as-prepared GaAs have been determined in the 400-1000 nm wavelength range using spectroscopic ellipsometry. These optical parameters are in agreement with the Bruggeman effective medium model. As has been found, the refractive index at 632 nm increases from 1.42 to 1.74 with increasing the film thickness from 52 to 154 nm and decreasing the porosity from 78 to 68 per cent.

Journal of Crystal Growth, 2002

In order to reduce the residual thermal stress in GaAs layer on Si substrate, we have introduced a porous region and a thin (B10 nm) Si layer over that in between GaAs and Si substrate. A 1-mm-thick undoped GaAs layers were grown by using chemical beam epitaxial technique at different temperatures. Because of the presence of porous region the morphology of the grown layers was slightly rough. Photoluminescence improvement and reduction of surface roughness have been achieved by chemical mechanical polishing (CMP). The ex situ non-contact optical interferometer observation shows that the rms roughness values of GaAs epilayer after CMP is 4.6 nm, whereas the as-grown is 9.5 nm. From the result of low-temperature photoluminescence, it was found that a significant reduction of the biaxial tensile stress has been achieved. The results prove that the growth of GaAs on Si substrate with intermediate porous region is a promising approach for obtaining GaAs epilayers with less biaxial tensile stress. r

MRS Proceedings, 1996

Porous structures on n-type GaAs (100) can be grown electrochemically in chloridecontaining solutions. Crystallographic etching of the sample is a precursor stage of the attack. Polarization curves reveal the existence of a critical onset potential for pore formation (PFP). The PFP is strongly dependent on the doping level of the sample and the presence of surface defects. Good agreement between the PFP and the breakdown voltage of the space charge layer is found. Surface analytical investigations by EDX, AES and XPS show that the porous structure consists mainly of GaAs and that anion uptake in the structure can only be observed after attack has been initiated. Photoluminescence measurements reveal – under certain conditions – visible light emission from the porous structure.

Nanoscale Research Letters, 2016

We have performed a detailed characterization study of electrochemically etched p-type GaAs in a hydrofluoric acid-based electrolyte. The samples were investigated and characterized through cathodoluminescence (CL), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that after electrochemical etching, the porous layer showed a major decrease in the CL intensity and a change in chemical composition and in the crystalline phase. Contrary to previous reports on p-GaAs porosification, which stated that the formed layer is composed of porous GaAs, we report evidence that the porous layer is in fact mainly constituted of porous As 2 O 3. Finally, a qualitative model is proposed to explain the porous As 2 O 3 layer formation on p-GaAs substrate.