Extrinsic Doping in Group IV Hexagonal-Diamond-Type Crystals

Amato, Michele; Kaewmaraya, Thanayut; Zobelli, Alberto

doi:10.1021/acs.jpcc.0c03713

Cited by 6 publications

(4 citation statements)

References 65 publications

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“…, ref for a discussion of the case of H in SiC). Notice, however, that whenever we compare the formation energy of a given impurity in the ZB or WZ crystal phase, μ X cancels out and thus, the conclusions do not depend on its exact value, as already shown in refs , . The same happens when comparing the formation energy of a dopant in the neutral and singly charged state, which determines the transition energy (neither the transition energy depends on μ X ).…”

Section: Methodssupporting

confidence: 54%

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Doping of III–V Arsenide and Phosphide Wurtzite Semiconductors

et al. 2020

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The formation energies of n-and p-type dopants in III−V arsenide and phosphide semiconductors (GaAs, GaP, and InP) are calculated within a first-principles total energy approach.Our findings indicate thatfor all the considered systemsboth the solubility and the shallowness of the dopant level depend on the crystal phase of the host material (wurtzite or zincblende) and are the result of a complex equilibrium between local structural distortion and electronic charge reorganization. In particular, in the case of acceptors, we demonstrate that impurities are always more stable in the wurtzite lattice with an associated transition energy smaller with respect to the zincblende case. Roughly speaking, this means that it is easier to p-type dope a wurtzite crystal and the charge carrier concentration at a given temperature and doping dose is larger in the wurtzite as well. As for donors, we show that neutral chalcogen impurities have no clear preference for a specific crystal phase, while charged chalcogen impurities favor substitution in the zincblende structure with a transition energy that is smaller when compared to the wurtzite case (thus, charge carriers are more easily thermally excited to the conduction band in the zincblende phase). ■ INTRODUCTIONCrystal-phase engineering is an emerging field in nanoscience that consists of the design of materials with tailor-made properties by growing ad hoc crystal phases. The interest in this field was boosted by the enormous progresses made in recent years in the growth of semiconducting nanowires (NWs) 1,2 and, specifically, by the fact that metastable crystal phases, which in bulk can only be obtained under extreme conditions of temperature and pressure, can be stabilized at room temperature and atmospheric pressure, thanks to a tight control of growth conditions. 3 Many III−V semiconductors, such as arsenides 4−7 and phosphides, 8−11 that in bulk only exhibit the zincblende (ZB) phase, can take the wurtzite (WZ) structure when grown as NWs. Similarly, Si and Ge group-IV semiconductors that in bulk have the 3C cubic-diamond crystal structure can be synthesized in the 2H hexagonal-diamond (i.e., lonsdaleite) polytype. 12−15 The possibility of growing semiconductors in different crystal phases is very appealing, as it might enable novel applications. 16 For instance, ZB GaP has an indirect band gap and thus a limited light emission efficiency, but in WZ GaP NWs, the band gap becomes direct, resulting in a strong photoluminescence. 9 Direct-band gap emission has also been predicted and reported in hexagonal Ge and SiGe alloys, 17,18 materials that have a notoriously poor light emission in the conventional cubic polytype adopted in the bulk. Moreover, in general, different polytypes can present different electronic, 7,19−21 optical, 22−26 and phononic properties. 27−31 48 Perhaps, the most ambitious (and exciting) goal of crystal-49 phase engineering is the design of complex structures by 50 working only (or mostly) with different polytypes of the same 51 material. The co...

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Section: Methodssupporting

confidence: 54%

“…The geometry of the doped supercells was optimized with a quasi-Newton algorithm until all the forces on the atoms were lower than 0.01 eV/Å. This computational setup proved to be accurate enough to give converged values of the formation energy, as shown in previous theoretical studies. − …”

Section: Methodsmentioning

confidence: 86%

Doping of III–V Arsenide and Phosphide Wurtzite Semiconductors

et al. 2020

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“…It will have great potential for innovative light sources implemented in MOEICs. In addition, it has been found that the group III dopant can be more easily introduced in the H–Ge due to the local C 3 v symmetry in comparison with the C–Ge. The H–Ge can even be stabilized by introducing carriers .…”

Section: Discussionmentioning

confidence: 99%

Hexagonal-Ge Nanostructures with Direct-Bandgap Emissions in a Si-Based Light-Emitting Metasurface

Zhang,

Yan,

Wang

et al. 2023

ACS Nano

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Si-based emitters have been of great interest as an ideal light source for monolithic optical-electronic integrated circuits (MOEICs) on Si substrates. However, the general Si-based material is a diamond structure of cubic lattice with an indirect band gap, which cannot emit light efficiently. Here, hexagonal-Ge (H–Ge) nanostructures within a light-emitting metasurface consisting of a cubic-SiGe nanodisk array are reported. The H–Ge nanostructure is naturally formed within the cubic-Ge epitaxially grown on Si (001) substrates due to the strain-induced nanoscale crystal structure transformation assisted by far-from-equilibrium growth conditions. The direct-bandgap features of H–Ge nanostructures are observed and discussed, including a rather strong and linearly power-dependent photoluminescence (PL) peak around 1562 nm at room temperature and temperature-insensitive PL spectrum near room temperature. Given the direct-bandgap nature, the heterostructure of H–Ge/C-Ge, and the compatibility with the sophisticated Si technology, the H–Ge nanostructure has great potential for innovative light sources and other functional devices, particularly in Si-based MOEICs.

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“…One mechanism is related to the relaxation of momentum conservation law due to the spatial confinement and Heisenberg uncertainty principle, being dominant in both Si and Ge NCs, and the other mechanism is the inter-valley coupling between direct and indirect states induced by the interface of the NC with the embedding matrix 23 . Another way of bandgap tuning is by tailoring its level of directness, as recently demonstrated direct bandgap light emission in Ge and GeSi nanowires with hexagonal structure 5 , 24 , and GeSi quantum dots 25 and also by infrared detection extended to longer wavelengths in NCs of direct bandgap GeSn alloys 26 .…”

Section: Introductionmentioning

confidence: 99%

Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Cojocaru

Lepadatu

Nemneş

et al. 2021

Sci Rep

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We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1−x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by ΔE(eV) = 0.651(1 − x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d1.25 for 2–4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1−x NC surface reaches the total number atoms of the Ge + Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.

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Extrinsic Doping in Group IV Hexagonal-Diamond-Type Crystals

Cited by 6 publications

References 65 publications

Doping of III–V Arsenide and Phosphide Wurtzite Semiconductors

Doping of III–V Arsenide and Phosphide Wurtzite Semiconductors

Hexagonal-Ge Nanostructures with Direct-Bandgap Emissions in a Si-Based Light-Emitting Metasurface

Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

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