Gettering or generation of the EL2 defects at dislocations in GaAs?

Figielski

1993

Acta Phys. Pol. A

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Experimental results are presented confirming that the two energy levels in GaAs: EE -0.68 eV and Ev + 0.37 eV, discovered in plastically deformed crystals, belong actually to dislocations. In view of recent identification of the electron state of misfit dislocations at an InGaAs/GaAs interface, a correspondence between these levels and dislocation types has been reinterpreted.The first mentioned leve1 belongs likely to α while the second one to fl dislocations of 60° (glide set) type. Such a correspondence is compatible with the observed effect of irradiation on dislocation glide motion in GaAs. It is also argued that these energy levels are involved in the phenomenon of unquenchability of the EL2 defects placed in high-stress regions near dislocations.

Section: Dislocation Electron States and Unquechability Of El2mentioning

confidence: 78%

Energy Levels and Electrical Activity of Dislocation Electron States in GaAs

Figielski

1993

Acta Phys. Pol. A

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“…To elucidate this correlation several mechanisms of dislocation-mediated generation of arsenic antisites have been proposed; cf. [26] and references therein. Similar mechanisms can occur for the N Ga defects in GaN resulting in their arrangement along dislocations, especially in the layers grown on sapphire and containing a large dislocation density of above 10 8 cm -2 .…”

Section: Dlts Resultsmentioning

confidence: 98%

Capture kinetics at deep‐level electron traps in GaN‐based laser diode

Yastrubchak

Phys. Status Solidi (c)

Mąkοsa

et al. 2007

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Two deep-level electron traps, E1 at E C − 0.23 eV and E2 at E C − 0.55 eV, have been revealed by means of deep-level transient spectroscopy (DLTS) in a GaN-based laser-diode heterostructure grown by metalorganic vapour-phase epitaxy on a bulk GaN substrate. The two traps represent different electron capture behaviours. The E1 trap, which exhibits the logarithmic capture kinetics and the DLTS-line shape characteristic of band-like electron states, is attributed to the core states of threading dislocations in a p-type layer of the structure. In contrast, the E2 trap, being the most prominent deep-level electron trap in GaN layers, displays the exponential capture kinetics and is assigned to isolated point defects, likely the nitrogen antisite defect.1 Introduction GaN-based III-V nitrides (GaN, InGaN and AlGaN) are wide direct band-gap semiconductors, which have already been applied successfully to optoelectronic devices, such as highbrightness blue light emitting diodes and lasers and solar-blind ultraviolet detectors [1]. Because of low thermal generation of charge carriers and large dielectric breakdown fields of these materials they have also found applications in high-temperature and high-power electronics [2]. However, owing to the large dislocation densities in the GaN epitaxial layers, commonly grown on highly-mismatched sapphire substrates, and self-compensation tendencies of wide band-gap semiconductors, a number of deep-level defects, affecting the performance and reliability of GaN-based devices, are usually present in the layers. Identification and understanding of these defects, especially dislocations, is of particular importance for improving the device technology.Deep-level transient spectroscopy (DLTS) is commonly used from already three decades as a powerful experimental technique for investigations of deep-level defects in semiconductor materials and structures. It allows characterizing and cataloguing deep levels by means of their capture cross-section and activation energy of thermal emission of charge carriers form the levels [3]. Additional information on the structure of deep-level defects can be gained while measuring the kinetics for capture of charge carriers into the defect states by means of recording the dependence of the DLTS-signal amplitude on the filling-pulse duration. In this respect, deep levels associated with extended defects, such as dislocations, distinctly differ from deep levels associated with isolated point defects or impurities, which exhibit exponential capture kinetics. On the contrary, deep levels related to dislocations are distinguished by logarithmic capture kinetics [4,5]. Such a kinetics results from the formation of a Coulombic barrier around the charged dislocations whose height increases with the filling-pulse duration [6].

“…First, incorporation of antimony into the Ga solution distinctly increases the ratio of the group V elements to gallium in the liquid. 7 Second, the EL2 defects can be created by moving dislocations 9 and a high density of misfit dislocations is actually generated at the interface during the epilayer growth. Third, the crystallization of our epilayers begins at the temperature of 850°C at which the maximum formation rate of the EL2 defects occurs.…”

Section: Deep Levels Caused By Misfit Dislocations In Gaassb/gaas Hetmentioning

confidence: 99%

Deep levels caused by misfit dislocations in GaAsSb/GaAs heterostructures

Applied Physics Letters

Mąkοsa

Figielski

et al. 1995

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Two deep electron traps induced by lattice mismatch in relaxed GaAs1−xSbx layers (x=0% to 3%) grown by liquid phase epitaxy (LPE) on GaAs substrates have been revealed by means of deep-level transient spectroscopy. One of the traps, that shows nonstandard, logarithmic capture kinetics and whose energy level is tied to the valence-band edge, has been related to electron states associated with α dislocations. The other trap has been attributed to the EL2 defect and possible reasons of its unexpected formation in the LPE-grown layers are briefly discussed.