13th International Conference on Defects--Recognition, Imaging and Physics in Semiconductors: Defects in Materials
Program Organizers: Marek Skowronski, Carnegie Mellon University; Robert Stahlbush, Naval Research Laboratory; Michael Dudley, State University of New York at Stony Brook
Thursday AM
September 17, 2009
Room: Glessner Auditorium
Location: Oglebay Resort and Conference Center
Session Chair: Jens Tomm, Max-Born-Institut
10:30 AM
Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm- Doped Potassium Rare Earth Double Tungstates and Their Influence on Laser Performance: Joan Carvajal1; Balaji Raghothamachar2; M Pujol1; X Mateos1; Michael Dudley2; Magdalena Aguiló1; Francesc Díaz1; 1Universitat Rovira i Virgili; 2Stony Brook University
Monoclinic potassium rare earth double tungstates, (KRE(WO4)2, RE = Y, Lu; KREW) are well suited as hosts for active lanthanide ion (Ln3+) dopants for diode-pumped solid state lasers, with particular interest in thin disk laser configurations when they are grown as thin films. Thin active layers are obtained by growing epitaxial structures of highly doped KREW by the LPE method on undoped KREW substrates sliced from TSSG-grown boules. Using synchrotron white beam X-ray topography (SWBXT), we have imaged defects and strain in bulk substrates of different rare earth tungstates as well as within Yb3+ and Tm3+ doped epitaxies grown on them. Surface preparation and defect distributions in the substrates are correlated with the quality of overgrown epitaxies. The effect of doping levels and the growth conditions on the quality and thickness of the epitaxies is analyzed and compared with lasing efficiency to optimize laser emission for future thin-disk laser configurations.
10:45 AM
Importance of the Surface for the Luminescence Stability of ZnO: Benjamin Dierre1; Xiaoli Yuan1; Nicola Armani2; Filippo Fabbri2; Giancarlo Salviati2; Kazuyuki Ueda3; Takashi Sekiguchi1; 1National Institute for Materials Science (NIMS); 2IMEM-CNR Institute; 3Toyota Technological Institute
Electron beam irradiation effects on the luminescence of ZnO crystal is a complicated problem. Indeed, a degradation of the ultraviolet luminescence usually occurs during cathodoluminescence (CL) measurements, but the degradation mechanisms have not been clarified yet. The evolution of the CL intensity strongly depends on the surface termination and the surface/volume ratio, which suggests that the surface plays a key role. To understand the role of the surface, we have treated the specimen by exposing atomic hydrogen and soaking on dilute HCl solution. The time-of-flight electron-stimulated desorption (TOF-ESD) measurements were performed to clarify the H+ and O+ ions desorption. We find that the desorption of adsorbed hydroxyl and H originated from H-passivated defects is the key to explain the luminescence evolutions. We suggest that the control of the surface by coating is one way to improve the lifetime of optoelectronic devices.
11:00 AM
Far-Field Imaging of Nanoscale Dislocation Pits by Forescatter Electron Detection for Investigating 4H-SiC Defect Behavior: Yoosuf Picard1; Robert Stahlbush1; Brenda VanMil1; Serguei Maximenko1; Rachel Myers-Ward1; Jaime Freitas1; D. Gaskill1; Charles Eddy1; Mark Twigg1; 1Naval Research Lab
Dislocations pose many problems for SiC-based devices. The ability to rapidly determine the position and identity of various dislocations in SiC is critical for converting, eliminating, or further characterizing them. Surface penetrating dislocations often produce characteristic shaped pits sub-micron in size and less than 100 nm deep. Forescatter electron detection (FED) is a simple strategy for enhancing topographic contrast in a scanning electron microscope sufficient to image and resolve these nanoscale pits. The FED approach is a straightforward, far-field imaging technique combining high angle tilting of the sample with appropriate diode detector positioning for recording low takeoff-angle electrons. The FED approach is coordinated with ultraviolet photoluminescence (UV-PL) to investigate the conversion behavior of BPDs to threading edge dislocations in 4H-SiC. Carrier diffusion lengths measured by the electron beam induced current (EBIC) technique are correlated to specific screw and edge dislocations delineated by the FED approach.
11:15 AM
Study of Metal Contamination in CMOS Image Sensors by Dark Current and Deep Level Transient Spectroscopies: Florian Domengie1; Jorge Luis Regolini2; Daniel Bauza3; 1STMicroelectronics/IMEP-LAHC; 2STMicroelectronics; 3IMEP-LAHC
CMOS Image Sensors (CIS’s) are receiving much attention for large volume electronic applications such as mobile phones, digital cameras, webcams, and automotive. CIS’s pixel scalability is reducing pixel size down towards 1.0 µm. A serious challenge is to introduce improvements in crucial parameters such as the dark current per pixel which is affected by defects incorporated during the whole process. In a manufacturing line, the process yield loss due to accidental metallic contamination is hard to assess and solve. In the present article we study the detection and characterization of gold and tungsten metallic contamination in CIS’s using Dark Current and Deep Level Transient Spectroscopies. Pixels are used to probe metal defects and observe electrical effects of individual atoms. Deep levels responsible for dark current are identified and their concentrations are calculated. Sensitivities of DCS and DLTS are evaluated to improve the defects detection capabilities available in production.
11:30 AM
Cathodoluminescence Study of InP Photonic Structures Fabricated by Dry Etching: Romain Chanson1; Juan Jimenez1; Frédéric Pommereau2; Jean-Pierre Landesman3; Ahmed Rhallabi3; 1University Valladolid; 2Alcatel-Thales III-V Laboratory; 3Institut des Matériaux Jean-Rouxel, CNRS and Nantes University
InP-based photonic structures fabricated by dry etching, standard reactive ion etching with CH4/H2, or high density – inductively coupled plasma etching with SiCl4, were studied by spectrally resolved cathodoluminescence. Rectangular waveguides (different widths and dielectric masks), were fabricated in bulk InP. We observed the formation of defects inside and around the waveguides. These defects are non radiative recombination centers, and also induce residual stresses. Defect and stress distributions were imaged by CL spectrum imaging. The stresses were compressive inside the waveguides and were associated with the defects generated at the interface between the InP and the dielectric mask. The influence of the dielectric mask and the geometry (aspect ratio) of the waveguides was studied, showing a clear relation between the stress and defect distribution. The results are analyzed in terms of the defect generation revealed by the CL images and the potential heating of the structures during the etching process.
11:45 AM
Ion-Implantation Control of Ferromagnetism in (Ga,Mn)As Epitaxial Layers: O. Yastrubchak1; J. Domagala2; J. Sadowski2; M. Kulik1; J. Zuk1; A. Toth3; R. Szymczak2; Tadeusz Wosinski2; 1UMCS, Institute of Physics; 2Institute of Physics, Polish Academy of Sciences; 3Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences
Epitaxial layers of (Ga,Mn)As ferromagnetic semiconductor have been subjected to low-energy low-dose ion implantation by applying both the chemically active oxygen ions and inactive ions of neon noble gas. A number of complementary characterization techniques have been used with the aim to study an effect of ion implantation on the layer properties. Investigation of their electrical and magnetic properties revealed that the implantation with either O or Ne ions completely suppressed both the conductivity and ferromagnetism in the layers. On the other hand, Raman spectroscopy measurements evidenced that O ion implantation influenced optical properties of the layers noticeably stronger than Ne ion implantation. Moreover, structural modifications of the layers caused by ion implantation were investigated using high-resolution X-ray diffraction technique. A mechanism responsible for ion-implantation induced suppression of ferromagnetism in (Ga,Mn)As layers, which could be applied as a method for tailoring nanostructures in the layers, is discussed.
12:00 PM
Study of Multilayer Semiconductor Structures by Local Methods: Maria Zamorynskaya1; Yana Domracheva1; Tatiana Popova1; Alexey Shakhmin1; Denis Shustov1; Alexander Trofimov1; Samuil Konnikov1; 1Ioffe Institute
In this paper we use complex of non-destructive local methods for characterization of multilayer semiconductor structures. Our latest investigation shows the possibility to measure the composition of layers on depth and of thin layers with thickness about sever nanometers by electron probe microanalysis. Simultaneous using of local cathodeluminescence allows characterization of point defects, charge carriers transport properties and their diffusion length. The rate of emission associated with quantum dots or quantum well layers with high charge carriers transport properties induces intensive luminescence related with this layer but weakly dependet on the electron beam energy. We use this method for the study of the laser heterostructures (ZnMgSSe-CdSe), a structure for HEMT transistors based on GaAs-AlxGa(1-x)As-InxGa(1-x)As and diode structures based on AlInGaN.
12:15 PM
Effects of Crystalline Strain and Defects in Electro-Optic Field Sensors: Anthony Garzarella1; Dong Ho Wu1; 1Naval Research Lab
Electro-optic (EO) sensors, used for the nonperturbative detection of electric fields, are strongly influenced by defects and strain in the nonlinear crystal. These effects can alter optical coherence of the probe beam, the nonlinear coefficient, and the effective value of the dielectric constant. In some cases, the optical modulation produced by the EO sensor is severely reduced, while in other cases, it can be enhanced by two orders of magnitude. In this report, we discuss these parasitic effects in detail, and how the can be exploited or suppressed to enhance the sensor responsivity.
12:30 PM Closing Remarks