Defects in Germanium

Weber, J. R.; Janotti, Anderson; Walle, Chris G. Van de

doi:10.1002/9783527650200.ch1

Cited by 12 publications

(19 citation statements)

References 69 publications

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“…Additionally, it has been shown that by tuning the HSE functional to reproduce the experimental bulk band gaps, the defect transition energetics relative to the band gap edges can be more accurately predicted. Such a tuned HSE functional has provided increased insight into a number of different defects 28,29,[39][40][41][42][43][44][45][46][47] . However, the physical justification for the tuning is unclear 41,48,49 and there is no guarantee that both delocalized bulk-like and localized defect-type states will be treated with equal accuracy using this approach.…”

Section: Introductionmentioning

confidence: 99%

Quasiparticle and hybrid density functional methods in defect studies: An application to the nitrogen vacancy in GaN

et al. 2017

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Defects in semiconductors can play a vital role in the performance of electronic devices, with native defects often dominating the electronic properties of the semiconductor. Understanding the relationship between structural defects and electronic function will be central to the design of new high-performance materials. In particular, it is necessary to quantitatively understand the energy and lifetime of electronic states associated with the defect. Here, we apply firstprinciples density functional theory (DFT) and many-body perturbation theory within the GW approximation to understand the nature and energy of the defect states associated with a charged nitrogen vacancy on the electronic properties of gallium nitride (GaN), as a model of a well-studied and important wide gap semiconductor grown with defects. We systematically investigate the sources of error associated with the GW approximation and the role of the underlying atomic structure on the predicted defect state energies. Additionally, analysis of the computed electronic density of states (DOS) reveals that there is one occupied defect state 0.2 eV below the valence band maximum and three unoccupied defect states at energy of 0.2-0.4 eV above the conduction band minimum, suggesting that this defect in the +1 charge state will not behave as a carrier trap. Furthermore, we compare the character and energy of the defect state obtained from GW and DFT using the HSE approximate density functional, and find excellent agreement. This systematic study provides a more complete understanding of how to obtain quantitative defect energy states in bulk semiconductors.

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Section: Introductionmentioning

confidence: 99%

Quasiparticle and hybrid density functional methods in defect studies: An application to the nitrogen vacancy in GaN

et al. 2017

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“…[12] By implanting ions into a semiconductor, its electronic properties can be tuned. [13], [14] However, the formation of defects during irradiation is a drawback of ion implantation as they may interfere with the dopants, create extended defects and even lead to amorphization. [15]- [17] Yet, amorphization can also be beneficial as channelling effects which occur in crystals may result in implantation profiles that are difficult to predict in crystalline materials.…”

Section: Introductionmentioning

confidence: 99%

Understanding amorphization mechanisms using ion irradiation in situ a TEM and 3D damage reconstruction

et al. 2019

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In this work, ion irradiations in-situ of a transmission electron microscope are performed on singlecrystal germanium specimens with either xenon, krypton, argon, neon or helium. Using analysis of selected area diffraction patterns and a custom implementation of the Stopping and Range of Ions in Matter (SRIM) within MATLAB (which allows both the 3D reconstruction of the collision cascades and the calculation of the density of vacancies) the mechanisms behind amorphization are revealed. An intriguing finding regarding the threshold displacements per atom (dpa) required for amorphization results from this study: even though the heavier ions generate more displacements than lighter ions, it is observed that the threshold dpa for amorphization is lower for the krypton-irradiated specimens than for the xenon-irradiated ones. The 3D reconstructions of the collision cascades show that this counter-intuitive observation is the consequence of a heterogeneous amorphization mechanism. Furthermore, it is also shown that such a heterogeneous process occurs even for helium ions, which, on average induce only three recoils per ion in the specimen. It is revealed that at relatively high dpa, the stochastic nature of the collision cascade ensures complete amorphization via the accumulation of large clusters of defects and even amorphous zones generated by single-heliumion strikes.

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“…[8]- [10] It is common to incorporate impurities acting as dopants to modify the electronic properties of semiconductors. [11] In order to incorporate the dopants in a precise manner, techniques are required to control their distribution within the host material. A standard technique to achieve this is ion implantation.…”

Section: Introductionmentioning

confidence: 99%

“…[6] To repair the crystal and to electrically activate the chemical dopants, an annealing step is often required. [6], [11] However, if an implanted single-crystal suffers amorphisation due to the ion irradiation then a residual crystalline seed is required to enable its recovery via solid-phase epitaxial growth (SPEG). [6], [12]- [14] Although ion implantation and subsequent recrystallisation via SPEG are well-established techniques in the processing of silicon, when studied in nanostructures significant differences have been observed compared to the bulk.…”

Section: Introductionmentioning

confidence: 99%

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Shape Modification of Germanium Nanowires during Ion Irradiation and Subsequent Solid‐Phase Epitaxial Growth

Camara

Hanif

Tunes

et al. 2018

Adv Materials Inter

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During ion irradiation which is often used for the purposes of band gap engineering, nanostructures can experience a phenomenon known as ion-induced bending (IIB). The mechanisms behind this permanent deformation are the subject of debate. In this work, germanium nanowires are irradiated with 30 or 70 keV xenon ions to induce bending either away from or towards the ion beam. By comparing experimental results with Monte-Carlo calculations, the direction of the bending is found to depend on the damage profile over the cross-section of the nanowire. After irradiation, the nanowires are annealed at temperatures up to 440°C triggering solid-phase epitaxial growth (SPEG) causing further modification to the deformed nanowires. After IIB, it is observed that nanowires which had bent away from the ion beam then straighten during SPEG whilst those which had bent towards the ion beam bend even more. This is attributed to differences in the mechanisms responsible for the ion-beam-induced bending in opposite directions. Thus, the results reported here give insights into the mechanisms causing the IIB of nanowires and demonstrate how to predict the evolution of nanowires under irradiation and annealing. Finally, they show that, under certain conditions, the bending can even be removed via SPEG.

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Defects in Germanium

Cited by 12 publications

References 69 publications

Quasiparticle and hybrid density functional methods in defect studies: An application to the nitrogen vacancy in GaN

Quasiparticle and hybrid density functional methods in defect studies: An application to the nitrogen vacancy in GaN

Understanding amorphization mechanisms using ion irradiation in situ a TEM and 3D damage reconstruction

Shape Modification of Germanium Nanowires during Ion Irradiation and Subsequent Solid‐Phase Epitaxial Growth

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