Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D41: Defects in OxidesFocus
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Sponsoring Units: DMP Chair: Hartwin Peelaers, University of Kansas Room: Room 319 |
Monday, March 6, 2023 3:00PM - 3:36PM |
D41.00001: Deep Acceptor Characterization in β-Ga2O3 Using Deep Level Optical Spectroscopy Methods Invited Speaker: Steve Ringel Deep acceptor doping is a standard process used in beta-phase gallium oxide (β-Ga2O3) electronic devices for compensating background electron concentrations to create semi-insulating component layers needed to enable high voltage and RF devices. Iron (Fe), magnesium (Mg) and nitrogen (N) are known candidate acceptors with Fe being most common. However, with its primary energy level at EC – 0.8 eV, associated with the FeGa defect, device biasing can modulate its charge state depending on device design. This can cause operational instabilities in b-Ga2O3 transistors. Here we are exploring the behavior of N doping as an alternative acceptor. Deep level optical spectroscopy (DLOS) measurements reveal its dominant energy level at EC – 2.9 eV, much deeper than Fe. However, since this position is below midgap, photocapacitance measurements based on excitation of trapped electrons to the conduction band are difficult to interpret due to competing hole emission to the valence band, which is always possible for photocapacitance studies of bandgap states with activation energies larger than EG/2. Here we explore this phenomenon in detail and compare with the more standard Fe characterization. We show evidence for simultaneous electron and hole emission from this N state, and we elucidate its complex effects on the observed DLOS data and their analysis, which can be erroneous if not accounted for correctly. We present and demonstrate a solution to this issue so that accurate DLOS characterization can be achieved. Through that process we show that N doping is extremely efficient dopant in b-Ga2O3. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D41.00002: Symmetry-breaking and reconstruction at point defects in solids Seán R Kavanagh, Irea Mosquera-Lois, Aron Walsh, David O Scanlon Point defects are a universal feature of crystalline materials. Their identification is often addressed by combining experimental measurements with theoretical models. The standard approach of simulating defects is, however, prone to miss the ground state atomic configurations associated with energy-lowering reconstructions from the idealised crystallographic environment.1–5 Missed ground states compromise the accuracy of calculated properties. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D41.00003: Electronic structure and band alignment of dilute III-V1-xBix alloys Abdul Saboor, Shoaib Khalid, Anderson Janotti Adding a few atomic percent of Bi to conventional III-V semiconductors leads to significant changes in their electronic structure and optical properties. Bismuth substituting on the pnictide site in III-Vs leads to an increase in spin-orbit splitting ?SO at the top of the valence band (Γ8 − Γ7) and a substantial reduction in band-gap. Quantifying these changes is key to designing and simulating electronic and optoelectronic devices. Using hybrid functional calculations, we predict the band-gap of III-Vs (III=Al, Ga, In and V=As, Sb) with low concentrations of Bi (3.125%, 6.25%) and the band alignment to their parent compounds. As expected, adding Bi raises the valence-band maximum (VBM); however, contrary to previous assumptions, the conduction-band minimum (CBM) is also significantly affected; both effects contribute, almost equally, to the sizeable band-gap reduction. These changes are predicted to be larger in the arsenides than in the antimonides, and explained in terms of atomic size and electronic mismatches. Our results provide accurate parameters and guiding principles for designing devices based on dilute III-V bismide alloys. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D41.00004: Donor-Acceptor pairs in wide-band-gap semiconductors for quantum technology applications Anil Bilgin, Ian N Hammock, Jeremy Estes, Hannes Bernien, Alexander A High, Giulia Galli Donor-acceptor pairs (DAP) in semiconductors, for example boron and nitrogen in diamond, exhibit large electric dipole moments which could enable optically controllable long-range interactions between separated pairs. These interactions would extend over a significantly longer length scale than spin-spin interactions, leading to new ways to connect quantum states in solids. Here, we carry out calculations based on density functional theory (DFT) to investigate the electronic structure and interactions of DAP formed by various substitutional defects in both diamond and SiC. We use the Quantum Espresso code to determine the most stable charge transition states by computing total energy formation diagrams and evaluate zero phonon lines using constrained DFT. In addition, an explicit correction integral for the emission energy of closely separated DAP is considered. Finally, we show that polarization differences between ground and excited states of DAP lead to their unusually large electric dipole moments both in diamond and SiC. Our results indicate that B-N pairs in diamond are challenging to control due to their large electron-phonon coupling while SiC appears to be a suitable candidate material for hosting DAP and to realize long-range optically controllable interactions. |
Monday, March 6, 2023 4:12PM - 4:24PM Author not Attending |
D41.00005: Stability and Optoelectronic Properties of Select Defects and Doping in Nickel Oxide Samuel R Cantrell, Luisa M Scolfaro, Pablo D Borges, Wilhelmus J Geerts Nickel oxide (NiO) is a transparent conducting oxide (TCO) that shows |
Monday, March 6, 2023 4:24PM - 4:36PM |
D41.00006: Theory of Charge Transfer Between Two Defects in a Wide-Bandgap Semiconductor Rodrick Kuate Defo, Alejandro W Rodriguez, Efthimios Kaxiras, Steven L Richardson Charge traps in the semiconductor bulk lead to difficulty in determining the electric field within wide-bandgap semiconductors. Given the large number of charge-trap candidates in the bulk, they are generally treated qualitatively or using generalized models. An accurate determination of the electric field within a wide-bandgap semiconductor is nonetheless important in predicting the operation of semiconductor devices and the performance of solid-state single-photon emitters embedded within the semiconductor devices. In this work, based on density-functional theory (DFT) and the theory of band bending, we quantitatively capture the average electric field measured at the location of NV- centers at the 15N+ average implantation depth of d = 35 nm for the commonly used oxygen-terminated diamond (see [D. A. Broadway et al., Nature Electronics 1, 502 (2018)]). We find that this average electric field is primarily determined by the neighboring substitutional N. Our work has the potential to aid in improving both the functioning of semiconductor devices and the performance of single-photon emitters embedded within the semiconductor devices. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D41.00007: Ab initio study of substitutional nitrogen in silicon: linking the defect to its spectroscopic properties Chloe Simha, Luigi Giacomazzi, Gabriela Herrero-Saboya, Layla Martin-Samos, Anne Hemeryck, Nicolas Richard Nitrogen impurities in silicon have proven to enhance its mechanical and chemical properties. They are also foreseen as promising candidates for qubits as they might enable room-temperature operations and are already compatible with existing industrial production lines. However, nitrogen is highly reactive in silicon. It recombines with vacancies and other impurities, thus resulting in the formation of a wide variety of defects and defect-complexes that can exist in different charge states. Such a diversity of defects leads to ambiguous experimental identification. Indeed, for the simple case of substitutional nitrogen, there is still an ongoing debate on its fundamental properties, such as the number and nature (shallow or deep) of its charge transition levels (CTL). In this work, we focus on the substitutional nitrogen impurity (NSi) and propose a theoretical model that bridges the atomic scale structure and its corresponding spectroscopic signature. We perform ab initio calculations to sample the potential energy surface of the NSi system. The resulting defect configurations are grounded in group theory considerations and linked to the pseudo Jahn-Teller effect. Moreover, we compute EPR parameters and CTL of NSi which allows for direct comparison with experiments (EPR/DLTS). |
Monday, March 6, 2023 4:48PM - 5:00PM |
D41.00008: Dependence of ZnO-based Phosphor Spectral Emission on UV and X-ray Excitation Pulse Width Eric R Westphal, Noelle M Collins, Linda E Hansen, Alan L Kastengren, Caroline Winters Emission from lanthanide or transition metal-doped ceramics—phosphors—is thermographic due to competition between radiative and non-radiative processes observed after excitation from either a UV (non-ionizing) or x-ray (ionizing) source. The mechanisms of excitation, non-radiative relaxation, and emission vary between the two excitation strategies: UV excitation causes emission from internal transitions of valence electrons that can decay via processes such as charge transfer states, and x-ray excitation causes core electron ejection and emission via electron-hole recombination pairs that may relax via phonon production. This work explores the effects that various ionizing and non-ionizing excitation sources have on the spectral properties of ZnO:Zn and ZnO:Ga. Results indicate that the spectral properties of ZnO:Ga remain invariant between continuous synchrotron x-ray excitation and pulsed UV laser excitation. However, ZnO:Zn spectral properties are shown to vary between sources of differing pulse durations. Spectra produced by this phosphor from a continuous synchrotron x-ray beam match those obtained from continuous UV excitation using a UV LED. The intensities of the present spectral lines vary dramatically from those observed for ZnO:Zn excited using a pulsed UV laser system. The implications of this variance in spectral properties of ZnO:Zn due to excitation pulse duration are discussed. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-14571 A |
Monday, March 6, 2023 5:00PM - 5:12PM |
D41.00009: Computational Prediction and Experimental Realisation of Earth-Abundant Transparent Conducting Oxide Ga-Doped ZnSb2O6 Joe Willis, David O Scanlon Transparent conducting oxides have become ubiquitous in modern opto-electronics. However, the number of oxides that are transparent to visible light and have the metallic-like conductivity necessary for applications is limited to a handful of systems that have been known for the past 40 years. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D41.00010: Role of hydrogen in gallium oxide Chris G Van de Walle, Mengen Wang, Sai Mu, Joel B Varley, John L Lyons, Darshana Wickramaratne The properties of gallium oxide make it particularly suitable for applications in power electronics. Hydrogen is often present during growth or processing of the material; in fact, in the widely used technique of metal-organic chemical vapor deposition (MOCVD) hydrogen is present in the metal-organic precursors and often used as a carrier gas. It is therefore important to assess the impact of hydrogen on growth and on the properties of Ga2O3 and related alloys. We address these issues using first-principles calculations based on density functional theory. Our comprehensive study of surface reconstructions establishes under which conditions hydrogen will be present on the surface, and how it will affect the growth. For hydrogen that gets incorporated in the material, we calculate diffusion barriers, which turn out to be highly anisotropic [1]. Hydrogen can also interact with intentional or unintentional impurities; I will discuss hydrogen passivation of dopants, and also address complex formation with carbon, another impurity that is easily incorporated during MOCVD growth. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D41.00011: Capture cross sections of point defects in semiconductors Xiaoguang Zhang, Guanzhi Li, Laura Nichols, Yue Yu, Andrew O'Hara, Georgios D Barmparis, Sokrates T Pantelides The treatment of multiphonon processes by which electronic energy is dissipated to the lattice has been hampered by an extremely rapid increase in the number of multiphonon configurations that can be formed as the number of included phonon modes is increased. Here, we employ the general theory developed in Ref. 1 for nonradiative capture of carriers by defects in semiconductors, based on density functional theory. We replace the Monte Carlo method of integrating over phonon modes with a much faster time-domain integration method that includes all phonon modes in the computational supercell. We also report results for both zeroth- and first-order contributions to carrier-capture cross sections in two cases: electron capture by a model Si dangling bond in a triply-hydrogenated vacancy in Si and hole capture by a CN substitutional impurity in GaN. |
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