IR laser-induced selective area functionalization of digital photocorrosion GaAs/AlGaAs biosensor

International audiencethird priz

FTIR and photoluminescence investigation of self-assembled monolayers of long-chain thiol on (001) GaAs

Peer reviewed: YesNRC publication: Ye

Intraband absorptions in GaN/AlN quantum dots in the wavelength range of 1.27-2.4 mu m

GaN/AlN quantum-dot superlattices grown by molecular-beam epitaxy on silicon (111) or sapphire (0001) substrate have been investigated using high-resolution transmission electron microscopy, photoluminescence, and photo-induced absorption spectroscopy. Under interband excitation at lambdaapproximate to351 nm, three resonances are observed, respectively peaked at 2.1 mum (2.36 mum), 1.46 mum (1.69 mum), and 1.28 mum (1.27 mum) for the sample grown on silicon (sapphire) substrate. We show that the absorptions involve conduction-band interlevel transitions from the ground state to p-like or d-like states, and that their energy is governed mainly by the magnitude of the internal field in the GaN dots. (C) 2003 American Institute of Physics

Spectroscopy of the electron states in self-organized GaN/AlN quantum dots

We present detailed analysis of inter- and intraband transitions in GaN/AlN self-organized quantum dots grown on sapphire, silicon (111) and 6H-SiC substrates. Samples containing quantum dots of different size were characterized by means of transmission electron microscopy, photoluminescence and photoinduced absorption spectroscopy. Interlevel transitions in the conduction band were identified in the 0.52-0.98 eV range covering the telecommunication wavelength band. The s-p(z), transition ranges from 0.52 eV to 0.8 eV for dots with height of 6 down to 1.5 nm, respectively. Experimental results are compared with theoretical calculations showing that in larger dots the transition energy is governed by the value of the internal field

Spectroscopy of intraband electron confinement in self-assembled GaN/AlN quantum dots

We present a detailed analysis of inter- and intraband transitions in GaN/AIN self-organized quantum dots grown on sapphire, silicon (111) and 6H-SiC substrates. Quantum dot samples have been characterized by means of transmission electron microscopy, photoluminescence and photo-induced absorption spectroscopy. Interlevel transitions in the conduction band are observed in the 0.52-0.98 eV energy range, thus covering the telecommunication band. The s-p(z) absorption is peaked at 0.8 eV (0.52 eV) for samples with dot height of 1.5 nm (6 nm). Calculations show that in bigger dots the transition energy is governed by the value of the internal field

Intraband spectroscopy of self-organized GaN/AlN quantum dots

GaN/AlN quantum dots grown by molecular beam epitaxy either on silicon (111), sapphire or 6H-SiC (0001) substrate have been investigated using photoluminescence, cathodoluminescence, Fourier transform infrared spectroscopy and attenuated total reflection spectroscopy. In-plane polarized intraband absorption is observed at energies of similar to 150 and 310 meV in GaN dots with 22 and 7.5 nm base diameter, respectively. For bigger dots, we observe three interlevel absorptions with a polarization component along the c-axis at energies ranging from 0.52 to 0.97 eV. Based on a simple 2D modelling of the confinement energies we show that the resonant absorptions involve conduction-band interlevel transitions between the electron ground state and states with one or two nodes along the c-axis and that in large dots, the internal field governs the transition energies. (C) 2002 Elsevier Science B.V. All rights reserved

Assessment of the Passivation Capabilities of Two Different Covalent Chemical Modifications on GaP(100)

Gallium phosphide is a semiconductor material that can be used for the fabrication of optoelectronic devices. The report compares the ability of two similar organic molecules to form covalent bonds with the GaP(100) surface. Undecenoic acid (UDA) is a terminal alkene that can potentially form Ga-C bonds, and mercaptoundecanoic acid (MUA) is a thiol that can be used to generate Ga-S bonds. The chemical passivation capabilities of the functionalized surfaces exposed to different media were investigated by contact angle measurements, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Toxicity levels, which are important for sensing applications. were evaluated by inductively coupled plasma mass spectrometry (ICP-MS) on the media in which surfaces were stored in order to identify any gallium leaching from the substrates. Both molecules formed fairly disordered monolayers demonstrated by comparable oxide thicknesses. The UDA molecules demonstrated better stability compared to MUA molecules based on contact angle measurements and tilt angle data extracted from XPS results. According to the XPS data, the UDA molecules formed a more dense adlayer compared to MUA molecules. With respect to toxicity, the UDA-functionalized GaP provided better passivation which was confirmed by less gallium leaching into water and saline solutions. Overall, the superior passivation provided by UDA demonstrates that alkene grafting has better potential for modifying GaP based devices such as implantable sensors