Response to "Comment on 'Carrier recombination near threading dislocations in GaN epilayers by low voltage cathodoluminescence'" [Appl. Phys. Lett. 97, 166101 (2010)]

Abstract : The authors are aware that there are number of theoretical models available to simulate cathodoluminescence (CL) contrast as a function of the distance, r, from a nonradiative defect. In our letter1 a simple expression, C(r)=C0 exp(−r/L)C(r)=C0 exp(−r/L), was chosen to compare the diffusion length, L, from GaN samples with different n-doping levels over a range of low electron beam energies. This approach is widely used in other studies of CL dislocation contrast as pointed out in the comment on the letter and it was found to provide an acceptable fit to the experimental CL contrast data

Carrier transport properties in the vicinity of single seld-assembled quantum dots determined by low-voltage cathodoluminescence imaging

Abstract : We propose a method to investigate the carrier transport properties in the ultrathin wetting layer of a self-assembled quantum dot (QD) structure using low-voltage cathodoluminescence (CL) imaging. Measurements are performed on diluted InAs/InP QDs in order to spatially resolve them on CL images at temperature ranging from 5 to 300 K. The mean ambipolar diffusion length extracted from CL intensity profiles across different isolated bright spots is about 300 nm at 300 K. This gives an ambipolar carrier mobility of about 110 cm2/(V s)110 cm2/(V s). Temperature investigation reveals a maximum diffusion length near 120 K

Raman study of As outgassing and damage induced by ion implantation in Zn-doped GaAs

Abstract : Room temperature micro-Raman investigations of LO phonon and LO phonon-plasmon coupling is used to study the AsAs outgassing mechanism and the disordering effects induced by ion implantation in ZnZn-doped GaAsGaAs with nominal doping level p=7×1018cm−3p=7×1018cm−3. The relative intensity of these two peaks is measured right after rapid vacuum thermal annealings (RVTA) between 200 and 450°C450°C, or after ion implantations carried out at energies of 40keV40keV with P+P+, and at 90 and 170keV170keV with As+As+. These intensities provide information regarding the Schottky barrier formation near the sample surface. Namely, the Raman signature of the depletion layer formation resulting from AsAs desorption is clearly observed in samples submitted to RVTA above 300°C300°C, and the depletion layer depths measured in ion implanted GaAs:ZnGaAs:Zn are consistent with the damage profiles obtained through Monte Carlo simulations. Ion channeling effects, maximized for a tilt angle set to 45°45° during implantation, are also investigated. These results show that the Raman spectroscopy is a versatile tool to study the defects induced by postgrowth processes in multilayered heterostructures, with probing range of about 100nm100nm in GaAsGaAs-based materials

Power dependent switching of nonlinear trapping by local photonic potentials

We study experimentally and numerically the nonlinear scattering of wave packets by local multi-site guiding centers embedded in a continuous dielectric medium, as a function of the input power and angle of incidence. The extent of trapping into the linear modes of different sites is manipulated as a function of both the input power and incidence angle, demonstrating power-controlled switching of nonlinear trapping by local photonic potentials.Comment: Submitted to Optics Letter

Enhancement of quantum well intermixing on InP/InGaAs/InGaAsP heterostructures using titanium oxide surface stressors to induce forced point defect diffusion

Quantum well intermixing was studied on InPInGaAsInGaAsP heterostructures under stress induced by a Ti Ox surface stressor. Results provide a comparison of thermal emission wavelength shift and effective emission wavelength shift for samples intermixed with and without applied stress. It is shown that Ti Ox decreases the measured thermal shift depending on the amplitude of the induced stress. It is also shown that the diffusion of point defects created during ion implantation prior to Ti Ox stressor deposition is significantly enhanced. This results in an increase of the effective wavelength shift by up to 300%. © 2006 American Institute of Physics.A. François, V. Aimez, J. Beauvais, M. Gendry and P. Regren

UV laser controlled quantum well intermixing in InAlGaAs/GaAs heterostructures

Abstract : The influence of surface irradiation of GaAs with a KrF excimer laser on the magnitude of the quantum well intermixing (QWI) effect has been investigated on GaAs/AlGaAs and GaAs/AlGaAs/InAlGaAs QWs heterostructures. The selective area irradiation through a SiOx mask was carried out in an atmospheric environment. Following the 1000 pulses irradiation at 100 mJ/cm2, the samples were annealed in a rapid thermal annealing furnace at 900 °C. Photoluminescence mapping and cathodoluminescence measurements show that significant laser-induced suppression of the QWI process can be achieved with lateral resolution of the order of 1μm

Optical spatial solitons at the interface between two dissimilar periodic media: Theory and experiment

Discrete spatial solitons traveling along the interface between two dissimilar one-dimensional arrays of waveguides were observed for the first time. Two interface solitons were found theoretically, each one with a peak in a different boundary channel. One evolves into a soliton from a linear mode at an array separation larger than a critical separation where-as the second soliton always exhibits a power threshold. These solitons exhibited different power thresholds which depended on the characteristics of the two lattices. For excitation of single channels near and at the boundary, the evolution behavior with propagation distance indicates that the solitons peaked near and at the interface experience an attractive potential on one side of the boundary, and a repulsive one on the opposite side. The power dependence of the solitons at variable distance from the boundary was found to be quite different on opposite sides of the interface and showed evidence for soliton switching between channels with increasing input power

Carrier recombination near threading dislocations in GaN epilayers by low voltage cathodoluminescence

The authors present a low voltage cathodoluminescence (CL) study of as grown GaN and GaN:Si epilayers on sapphire. At 1 kV they resolve individual threading dislocations on the sample surface at low temperature (5 K), which appear as correlated dark spots. Analysis of CL intensity profiles across individual dislocation cores provides a direct measurement of the exciton and minority carrier diffusion lengths. Using this approach at 5 K, an exciton diffusion length of 62?28 nm was found for GaN:Si (~3?1018 cm?3) compared with 81?20 nm for a nominally undoped n-type GaN (~1?1016 cm?3

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Carrier diffusion processes near threading dislocations in GaN and GaN:Si characterized by low voltage cathodoluminescence

We present a low temperature study of GaN epilayers by means of low voltage cathodoluminescence (CL). We show that lowering the primary electrons accelerating voltage down to 1 kV allows imaging of single threading dislocations. By using monochromatic or panchromatic low voltage CL microscopy, it is possible to extract different diffusion lengths related to free excitons, bound excitons or donor-to-acceptor pair transitions. © 2006 Elsevier Ltd. All rights reserved