Tutorial: Defects in semiconductors—Combining experiment and theory

Alkauskas, Audrius; McCluskey, M. D.; Walle, Chris G. Van de

doi:10.1063/1.4948245

Cited by 357 publications

(253 citation statements)

References 85 publications

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“…For example, we clearly identified the temporal and spectral signatures of short-lived highly nonthermal initial carriers and the longer-lived thermalizing carriers near the Fermi level in plasmonic nanoparticles. By demonstrating the predictive capabilities of our theory for metal nanoparticles, we open up the field for similar studies in other materials [53] where fits are not necessarily possible or even reliable, e.g., semiconductor plasmonics, and where ab initio theory of ultrafast dynamics will be indispensable. …”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 90%

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

et al. 2017

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Ultrafast pump-probe measurements of plasmonic nanostructures probe the nonequilibrium behavior of excited carriers, which involves several competing effects obscured in typical empirical analyses. Here we present pump-probe measurements of plasmonic nanoparticles along with a complete theoretical description based on first-principles calculations of carrier dynamics and optical response, free of any fitting parameters. We account for detailed electronic-structure effects in the density of states, excited carrier distributions, electron-phonon coupling, and dielectric functions that allow us to avoid effective electron temperature approximations. Using this calculation method, we obtain excellent quantitative agreement with spectral and temporal features in transient-absorption measurements. In both our experiments and calculations, we identify the two major contributions of the initial response with distinct signatures: short-lived highly nonthermal excited carriers and longer-lived thermalizing carriers. DOI: 10.1103/PhysRevLett.118.087401 Plasmonic hot carriers provide tremendous opportunities for combining efficient light capture with energy conversion [1][2][3][4][5] and catalysis [6,7] at the nanoscale [8][9][10]. The microscopic mechanisms in plasmon decays across various energy, length, and time scales are still a subject of considerable debate, as seen in recent experimental [11,12] and theoretical literature [13][14][15][16]. The decay of surface plasmons generates hot carriers through several mechanisms, including direct interband transitions, phonon-assisted intraband transitions, and geometry-assisted intraband transitions, as we have shown in previous work [17,18].Dynamics of hot carriers are typically studied via ultrafast pump-probe measurements of plasmonic nanostructures using a high-intensity laser pulse to excite a large number of electrons and measure the optical response as a function of time using a delayed probe pulse [11,[19][20][21][22][23][24][25]. Various studies have taken advantage of this technique to investigate electron-electron scattering, electron-phonon coupling, and electronic transport [20,22,[26][27][28][29][30][31][32]. Figure 1 shows a representative map of the differential extinction cross section as a function of pump-probe delay time and probe wavelength. With an increase in electron temperature, the real part of the dielectric function near the resonant frequency becomes more negative, while the imaginary part increases [33]. This causes the resonance to broaden and blueshift at short times as the electron temperature rises rapidly, and then to narrow and shift back over longer times as electrons cool down, consistent with previous observations [34]. Taking a slice of the map at one probe wavelength reveals the temporal behavior of the electron relaxation [ Fig. 1(b)], whereas a slice of the map at one time gives the spectral response, as shown in Fig. 1(a) for a set of times relative to the delay time with maximum signal, t max ¼ 700 fs.Conventional analyses of pu...

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Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 90%

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

et al. 2017

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“…There is no hole present for V 3À Ga (all defect states are filled), and all nearest neighbors move outwards by 7-9% of the GaN bond length. This leads to large relaxation energies (also known as the Franck-Condon shift 29 ) of approximately 0.5 eV, and this in turn leads to the peak absorption (3.25 eV) and emission (2.27 eV) energies being significantly shifted from the zero-phonon line (ZPL; 2.80 eV), as shown in Fig. 5b.…”

Section: àmentioning

confidence: 99%

“…As outlined in ref. 29, such transitions can be described through the construction of a configuration-coordinate (CC) diagram, which describes how the energy of specific charge states depends on the changes in coordinates that occur when atomic relaxations are different for each of the charge states. Peak optical transition energies (either in absorption or emission processes) will then differ from the thermodynamic transition level by the Franck-Condon (FC) shift.…”

Section: Introductionmentioning

confidence: 99%

Computationally predicted energies and properties of defects in GaN

2017

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Recent developments in theoretical techniques have significantly improved the predictive power of density-functional-based calculations. In this review, we discuss how such advancements have enabled improved understanding of native point defects in GaN. We review the methodologies for the calculation of point defects, and discuss how techniques for overcoming the band-gap problem of density functional theory affect native defect calculations. In particular, we examine to what extent calculations performed with semilocal functionals (such as the generalized gradient approximation), combined with correction schemes, can produce accurate results. The properties of vacancy, interstitial, and antisite defects in GaN are described, as well as their interaction with common impurities. We also connect the first-principles results to experimental observations, and discuss how native defects and their complexes impact the performance of nitride devices. Overall, we find that lower-cost functionals, such as the generalized gradient approximation, combined with band-edge correction schemes can produce results that are qualitatively correct. However, important physics may be missed in some important cases, particularly for optical transitions and when carrier localization occurs.

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“…A previous tutorial paper in this series has discussed recent developments in combining theory and experiment in relation to defects. 10 In the following tutorial review we consider the principles and experimental techniques of junction spectroscopy together with specific issues related to the application of theory to the interpretation of junction spectroscopy experiments.…”

Section: This Was Dramatically Simplified In 1974 By Lang With the Inmentioning

confidence: 99%

Tutorial: Junction spectroscopy techniques and deep-level defects in semiconductors

Peaker

Markevich

Coutinho

2018

Journal of Applied Physics

103

107

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The term junction spectroscopy embraces a wide range of techniques used to explore the properties of semiconductor materials and semiconductor devices. In this tutorial review we describe the most widely used junction spectroscopy approaches for characterizing deep-level defects in semiconductors and present some of the early work on which the principles of today's methodology are based. We outline ab-initio calculations of defect properties and give examples of how density functional theory in conjunction with formation energy and marker methods can be used to guide the interpretation of experimental results. We review recombination, generation and trapping of charge carriers associated with defects. We consider thermally driven emission and capture and describe the techniques of Deep Level Transient Spectroscopy (DLTS), high resolution Laplace DLTS, admittance spectroscopy and scanning DLTS. For the study of minority carrier related processes and wide gap materials we consider Minority Carrier Transient Spectroscopy (MCTS), Optical DLTS (ODLTS and DLOS) together with some of their many variants. Capacitance, current and conductance measurements enable carrier exchange processes associated with the defects to be detected. We explain how these methods are used in order to understand the behaviour of point defects, the determination of charge states and negative-U (Hubbard correlation energy) behaviour. We provide, or reference, examples from a wide range of materials including Si, SiGe, GaAs, GaP, GaN, InGaN, InAlN and ZnO.

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Tutorial: Defects in semiconductors—Combining experiment and theory

Cited by 357 publications

References 85 publications

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

Computationally predicted energies and properties of defects in GaN

Tutorial: Junction spectroscopy techniques and deep-level defects in semiconductors

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