Defect-Related Current Instabilities in InAs/GaAs and AlGaAs/GaAs Structures? (original) (raw)
Related papers
Current instabilities in GaAs/InAs quantum dot structures
International Conference on Solid State Crystals 2000: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, 2001
Unexpected excess current was obtained in GaAs/InAs quantum dot structures at low temperatures and low current levels. This excess current exhibited instabilities with changing the bias, and over the time. It has been concluded that the excess current is a minority injection current connected with the high recombination rate through quantum dots. The instabilities are connected with unstable charge accupation of quantum dots.
Current instabilities in GaAs/InAs self-aggregated quantum dot structures
Applied Surface Science, 2002
Excess current was obtained in GaAs/InAs quantum dot structures at low temperatures and low current levels. This excess current exhibited instabilities with changing the bias, and over the time. It has been concluded that the excess current is a minority injection current connected with recombination through defects originated from the formation of QDs. The instabilities are connected with unstable occupation of energy levels induced by the above defects, which depend on temperature and on the current level. #
Instability of electrical characteristics of GaAs/InAs quantum dot structures
physica status solidi (c), 2005
We report on GaAs samples containing an InAs quantum dot matrix grown from 3 monolayers of InAs. In this case, most of the mechanical stress relaxes by misfit dislocations. Capacitance measurements have been performed on macroscopic devices and, also, from a scanning microscope in which the capacitance is measured between the probe and sample surface. It was found that the electrical characteristics dramatically change during the capacitance measurements. This is explained by a degradation of the quantum dot layer which is attributed to the generation of point defects and/or dislocations. These results draw attention to the fact that, at the microscopic scale measurement, a small current may result in a large local current density which, in turn, degrades the device.
Electrical characterization of InAs/GaAs quantum dot structures
Materials Science and Engineering: C, 2006
The electrical properties of InAs quantum dots (QD) in InAs/GaAs structures have been investigated by space charge spectroscopy techniques, current-voltage and capacitance-voltage measurements. Au/GaAs/InAs(QD)/GaAs Schottky barriers as well as ohmic/GaAs/ InAs(QD)/GaAs/ohmic structures have been prepared in order to analyze the apparent free carrier concentration profiles across the QD plane, the electronic levels around the QD and the electrical properties of the GaAs/InAs(QD)/GaAs heterojunction. Accumulation and/or depletion of free carriers at the QD plane have been observed by Capacitance-Voltage (C-V) measurements depending on the structure parameters and growth procedures. Similarly, quantum dot levels which exhibit distributions in energy have been detected by Deep Level Transient Spectroscopy (DLTS) and Admittance Spectroscopy (AS) measurements only on particular structures. Finally, the rectification properties of the InAs/GaAs heterojunction have been investigated and the influence of the related capacitance on the measured capacitance has been evidenced.
Semiconductors, 2014
Electron microscopy studies of GaAs structures grown by the method of molecular beam epitaxy and containing arrays of semiconductor InAs quantum dots and metallic As quantum dots are performed. An array of InAs quantum dots is formed using the Stranski-Krastanow mechanism and consists of five layers of vertically conjugated quantum dots divided by a 5 nm thick GaAs spacer layer. The array of As quantum dots is formed in an As enriched GaAs layer grown at a low temperature above an array of InAs quantum dots using postgrowth annealing at temperatures of 400-600°C for 15 min. It is found that, during the course of structure growth near the InAs quantum dots, misfit defects are formed; these defects are represented by 60°o r edge dislocations located in the heterointerface plane of the semiconductor quantum dots and penetrating to the surface through a layer of "low temperature" GaAs. The presence of such structural defects leads to the formation of As quantum dots in the vicinity of the middle of the InAs conjugated quantum dots beyond the layer of "low temperature" GaAs.
Study of electrically active defects in GaAs/InAs/GaAs QDs structures by DLTS and TEM
2006
The apparent C-V profiles and the deep levels in GaAs InAs GaAs quantum dot nanostructure, have been investigated by space charge spectroscopy techniques (C-V and DLTS). Accumulation peaks and/or depletion offree carriers at the QDs plane are observed under the considered growth parameters. It is shown that, both in the cap and at the QD-layerlcap interface, the deposition ofInAs QDs induces deep levels which exhibit a logarithmic dependence of the DLTS signal amplitude from the pulse width. Transmission Electron Microscopy (TEM) analysis shows extended defects in the cap and near the QD/cap interface, which have been correlated to electrical measurement results.
Lateral conductivity in GaAs/InAs quantum dot structures
The European Physical Journal Applied Physics, 2004
Lateral conductivity effects have been investigated in self-organised InAs quantum dot (QD) structures grown in a GaAs matrix with different cap layers. Current-voltage (I-V), capacitance-voltage (C-V), DLTS, capacitance and conductance frequency dependence, fast defect transient (FDT), and electron beam induced conductivity (EBIC) measurements were applied. The conductivity in the QD plane decays within a distance of 10 microns. The capacitance transients are dominated by the local QD-plane transversal conductivity and by the free carrier transport in the cap layer. The nonequilibrium free carrier created by electron beam excitation develop a potential barrier at macroscopic distances from the electrical contacts.
Defects in nanostructures with ripened InAs/GaAs quantum dots
Journal of Materials Science: Materials in Electronics, 2008
InAs/GaAs quantum dot (QD) structures were grown by molecular beam epitaxy (MBE) with InAs coverages h continuously graded from 1.5 ML to 2.9 ML. A critical coverage of 2.23 ML is found, above which the islands undergo ripening, which causes a fraction of quantum dots to increase in size and to eventually relax through the formation of pure, edge-type misfit dislocations which propagate towards the surface in the form of V-shaped defects. Concomitant with ripening, extendeddefect related traps with activation energies of 0.52 and 0.84 eV were observed, and regarded as the cause of the significant worsening of the optical and electrical properties in high coverage structures. Their relationship with the observed dislocations is discussed.