First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - <b>β</b>2(2x4)

Bacuyag, Dhonny; Escaño, Mary Clare Sison; David, Melanie; Tani, Masahiko

doi:10.1063/1.5020188

Cited by 17 publications

(6 citation statements)

References 53 publications

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“…The formation of such levels was found in Ref. [22] by DFT calculations. In the SI GaAs:EL2 sample, these defect states increased the compensation level, slightly increasing the concentration of active hole traps, but the concentration of SRH recombination centers increased, leading to a charge carrier lifetime reduction (Figure 4a).…”

Section: Discussionmentioning

confidence: 64%

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

et al. 2021

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The time dynamics of nonequilibrium charge carrier relaxation processes in SI GaAs:EL2 (semi-insulating gallium arsenide compensated with EL2 centers) and HR GaAs:Cr (high-resistive gallium arsenide compensated with chromium) were studied by the optical pump–terahertz probe technique. Charge carrier lifetimes and contributions from various recombination mechanisms were determined at different injection levels using the model, which takes into account the influence of surface and volume Shockley–Read–Hall (SRH) recombination, interband radiative transitions and interband and trap-assisted Auger recombination. It was found that, in most cases for HR GaAs:Cr and SI GaAs:EL2, Auger recombination mechanisms make the largest contribution to the recombination rate of nonequilibrium charge carriers at injection levels above ~(0.5–3)·1018 cm−3, typical of pump–probe experiments. At a lower photogenerated charge carrier concentration, the SRH recombination prevails. The derived charge carrier lifetimes, due to the SRH recombination, are approximately 1.5 and 25 ns in HR GaAs:Cr and SI GaAs:EL2, respectively. These values are closer to but still lower than the values determined by photoluminescence decay or charge collection efficiency measurements at low injection levels. The obtained results indicate the importance of a proper experimental data analysis when applying terahertz time-resolved spectroscopy to the determination of charge carrier lifetimes in semiconductor crystals intended for the fabrication of devices working at lower injection levels than those at measurements by the optical pump–terahertz probe technique. It was found that the charge carrier lifetime in HR GaAs:Cr is lower than that in SI GaAs:EL2 at injection levels > 1016 cm−3.

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Section: Discussionmentioning

confidence: 64%

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

et al. 2021

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“…In other words, a clean III-V(110) surface does not cause extra electron levels in the middle of the bulk band gap, in contrast to Si(100)(2 × 1) or Si(111)(7 × 7). In fact, the band gap without surface-related electron levels is a rather common property among clean III-V surfaces where the group-V dangling bonds become filled by electrons while group-III dangling bonds are empty [140][141][142][143][144]. In contrast, intrinsic point defects like As substitutional in Ga site (As Ga ) cause the midgap levels in the clean surfaces [144].…”

Section: Some Fundamental Properties Of Clean Iii-v Surfacesmentioning

confidence: 99%

Bridging the gap between surface physics and photonics

Laukkanen,

Punkkinen,

Kuzmin

et al. 2024

Rep. Prog. Phys.

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Use and performance criteria of photonic devices increase in various application areas such as information and communication, lighting, and photovoltaics. In many current and future photonic devices, surfaces of a semiconductor crystal are a weak part causing significant photo-electric losses and malfunctions in applications. These surface challenges, many of which arise from material defects at semiconductor surfaces, include signal attenuation in waveguides, light absorption in light emitting diodes, non-radiative recombination of carriers in solar cells, leakage (dark) current of photodiodes, and light reflection at solar cell interfaces for instance. To reduce harmful surface effects, the optical and electrical passivation of devices has been developed for several decades, especially with the methods of semiconductor technology. Because atomic scale control and knowledge of surface-related phenomena have become relevant to increase the performance of different devices, it might be useful to enhance the bridging of surface physics to photonics. Toward that target, we review some evolving research subjects with open questions and possible solutions, which hopefully provide example connecting points between photonic device passivation and surface physics. One question is related to the properties of the wet chemically cleaned semiconductor surfaces which are typically utilized in device manufacturing processes, but which appear to be different from crystalline surfaces studied in ultrahigh vacuum by physicists. In devices, a defective semiconductor surface often lies at an embedded interface formed by a thin metal or insulator film grown on the semiconductor crystal, which makes the measurements of its atomic and electronic structures difficult. To understand these interface properties, it is essential to combine quantum mechanical simulation methods. This review also covers metal-semiconductor interfaces which are included in most photonic devices to transmit electric carriers to the semiconductor structure. Low-resistive and passivated contacts with an ultrathin tunnelling barrier are an emergent solution to control electrical losses in photonic devices.

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“…For the below-bandgap photoexcitation of both substrates, we considered the two-step photoabsorption via midgap states as proposed by Tani et al [14]. Mid-gap states arise from high density of EL2-like defects [18,19]. Published work reported that the transition energy from valence band to mid-gap states is about 0.8 eV [33], hence, laser excitation with λ = 1.55 µm (below-bandgap) is plausible.…”

Section: Numerical Modelmentioning

confidence: 99%

“…Similarly, Ramer, et al generated and detected terahertz radiation and attributed the THz radiation mechanism to the two-step photoabsorption process citing the proposed superlinear power law [13]. Presence of surface mid-gap states from As-antisite defects in LT-GaAs were recently revealed via scanning tunneling microscopy, and ab initio calculations [18,19]. Escaño et al concluded that these As-antisites could have facilitated the two-step photoabsorption process which resulted to THz emission/detection [19].…”

Section: Introductionmentioning

confidence: 99%

Terahertz emission mechanisms in low-temperature-grown and semi-insulating gallium arsenide photoconductive antenna devices excited at above- and below-bandgap photon energies

F Dela Rosa,

Publico,

F Cabello

et al. 2024

Semicond. Sci. Technol.

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In this work, the terahertz (THz) time-domain spectroscopy was employed in studying the carrier dynamics in low-temperature grown (LT-) and semi-insulating (SI-) gallium arsenide (GaAs) photoconductive antenna (PCA) at above- (λ = 780 nm, Eg = 1.59 eV) and below- (λ = 1.55 μm, Eg 0.80 eV) bandgap excitation. We measured the excitation power dependence of the LT-GaAs (SI-GaAs) THz emission. Then,the equivalent circuit model (ECM) which considers the (i) photogeneration, (ii) screening effects, and (iii) transport of carriers was utilized in analyzing the THz radiation mechanisms in the above- and below-bandgap excitation of the two substrates. In simulating the above-bandgap THz emission of both PCAs, we employed the direct bandgap excitation model which takes into account theband-to-band transitions of photoexcited carriers. Meanwhile, to simulate the LT-GaAs (SI-GaAs) THz emission at below-bandgap excitation we utilized the two-step photoabsporption facilitated by the mid-gap states. In this model thephotoexcited carriers jump from the valence band to the mid-gap states and then to the conduction band. Results suggest that the THz emission from LT-GaAs and SI-GaAs at above- and below-bandgap excitation occur due to band-to-bandtransitions, and two-step photoabsorption process via midgap states, respectively.

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First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - β2(2x4)

Cited by 17 publications

References 53 publications

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

Bridging the gap between surface physics and photonics

Terahertz emission mechanisms in low-temperature-grown and semi-insulating gallium arsenide photoconductive antenna devices excited at above- and below-bandgap photon energies

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