Vacuum 171 (2020) 108976 Available online 3 October 2019 0042-207X/© 2019 Elsevier Ltd. All rights reserved. Optical properties of porous GaAs formed by low energy ion implantation Ang� elica Hern� andez a, * , Yuriy Kudriavtsev a, b , Cecilia Salinas-Fuentes b , Carlos Hern� andez-Gutierrez b , Rene Asomoza a a Solid State Electronics Section, Electrical Engineering Department, Center for Research and Advanced Studies form National Polytechnic Institute, CINVESTAV-IPN, Av. IPN n. 2508, Col. San Pedro Zacatenco, Mexico City, C.P. 07360, Mexico b Nanoscience and Nanotechnology Doctorate Program, Center for Research and Advanced Studies form National Polytechnic Institute, CINVESTAV-IPN, Av. IPN n. 2508, Col. San Pedro Zacatenco, Mexico City, C.P. 07360, Mexico A R T I C L E INFO Keywords: Ion implantation Visible luminescence Porous GaAs ABSTRACT We report about chemical, structural and optical characteristics of porous GaAs near-surface layers formed by low energy and high fuence ion implantation of Si þ and Ge þ ions. The energy of implanted ions was 25 keV and the ion dose was 2 � 10 16 ion⋅cm 2 for both species. After implantation, experimental samples were annealed under N 2 atmosphere resulting in the increment of porosity. The chemical properties of the samples were studied by SIMS and Raman spectroscopy. The Raman spectroscopy was used as well for examining the presence of amorphous phase in a near surface layer caused by ion implantation. The porous GaAs demonstrates visible photoluminescence under ultraviolet excitation. Optical refection coeffcient radically decreases after implan- tation due to the porous layer formation. The size and in-depth distribution of pores were analyzed by AFM in combination with controlling Ar þ ion etching. Our fndings, let us suggests that ion implantation can be used as a reliable technique to prepare porous semiconductors with potential applications for fabrication of optoelectronic devices. The mechanism of pores formation and growth during ion implantation in semiconductors and post- implantation annealing is discussed. 1. -Introduction Ion implantation has been widely used in the semiconductor industry during decades to form electrically active layers (p- and n-type) practi- cally in any semiconductor. The typical ion energy used for the im- plantation has varied from 30 keV (for light elements) to 300 keV (for heavy elements). Computer simulations, based on the Monte Carlo method, demonstrate in many cases a good coincidence with experi- mentally measured ion distributions. For ion implantation systems, the vacuum levels need to be maintained below 10 5 mbar, also contami- nation should be less than 100 particles per m 2 . Otherwise, the presence of load gas in the implantation chamber turns into unwanted dopant vapors that can easily outgassing from implanted surfaces [1,2]. The development of vacuum technologies for ion implantation avoided problems such as contamination, wafer charging and beam transport, see reference [3] and references therein. It is well known about formation of point defects due to implanta- tion; this can result in amorphization (partial or complete) of a near surface layer. At the same time, many investigators published data demonstrating formation of undersurface pores among other defects in semiconductors during ion implantation [4–11]. This occurs when the ion fuence exceeds some critical values, which depending on implan- tation regime and target composition used. Different size of pores and break of crystalline structure at porous surfaces resulting in a formation of nano-crystallites structures. This leads to the visible luminescence in the spectral range of 400–800 nm (photoluminescence) with different wavelengths from porous layers reported by different authors [4,10,12]. So, porous layer can be considered as active layers for new generation of solar cells and white light emitting diodes. These results stimulated in- terests in fabrication of porous silicon and germanium, the semi- conductors with indirect bandgaps, in order to use them as a material for optoelectronics [12–14]. To the moment there is no any quantitative model describing pores formation during implantation and their dy- namics depending on the ion fuence and the temperature of post-annealing treatment, probably because of a lack of systematic experimental data obtained for various semiconductors and for various experimental regimes. In last two decades a strong interest in semiconductor industry was * Corresponding author. E-mail address: ghernandez@cinvestav.mx (A. Hern� andez). Contents lists available at ScienceDirect Vacuum journal homepage: http://www.elsevier.com/locate/vacuum https://doi.org/10.1016/j.vacuum.2019.108976 Received 8 July 2019; Received in revised form 17 September 2019; Accepted 27 September 2019