Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D67: Defects in Nitride MaterialsFocus Recordings Available
|
Hide Abstracts |
Sponsoring Units: DMP Chair: Elif Ertekin, U Illinois Room: Hyatt Regency Hotel -Hyde Park |
Monday, March 14, 2022 3:00PM - 3:36PM |
D67.00001: First-principles calculations of point defects and impurities in nitride semiconductors Invited Speaker: Darshana Wickramaratne III-nitride semiconductors (GaN, AlN, InN) and their alloys have enabled tremendous progress in a range of applications from wide-bandgap (WBG) power electronics to light-emitting devices. Native point defects and impurities play an important role in hindering or aiding in the success of these applications. Better control of point defects is still needed in order to improve materials quality and enable improved efficiency of devices. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D67.00002: Modeling of color tunable light-emitting diodes with Eu-doped GaN active layers Hayley J Austin, Brandon Mitchell, Jun Tatebayashi, Yasufumi Fujiwara, Volkmar G Dierolf It has been demonstrated that gallium nitride (GaN) based LED devices with active Europium-doped Gallium Nitride (GaN:Eu) layers can be tuned under current injection from red to orange to yellow. This tuning is achieved by changing current density under continuous excitation or by adjusting the duty cycle and amplitude of pulse-width modulated pulsed excitation. The underlying mechanism is a redistribution of energy among 5DJ states of the Eu3+ ion through energy shuffling that involves a local defect. This shuffling among different excitation states is possible due to the wide range in time scales (10ps to 200µs) of the relevant processes within this defect complex. To quantitatively model this behavior, we extended previous modeling work by including the local defect. As a result, we can predict red-yellow tunability by looking at the relative average populations of the Eu’s 5D0 and 5D1 states and using color mixing of red emission from the 5D0 state with green emission from the 5D1 state. Furthermore, by considering the defect as able to emit light in the blue spectral region, our model can predict tunability parameters within a larger color space due to the mixing of three distinct colors: red, green, and blue. A specific candidate for such a defect would be a Si-Mg complex. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D67.00003: Deterministic creation of optically active defects in AlN towards integrated single photon emitters Heejun Byeon, Michael D Titze, Jacob D Henshaw, Deanna M Campbell, Peter A Schultz, George T Wang, Edward Bielejec, Michael P Lilly, Andrew M Mounce Single photon emitters (SPEs) are fundamental building blocks for photonic-based quantum communication, quantum cryptography, and quantum computation. Recently, wide-bandgap compound semiconductor AlN has attracted great interest as potential host materials for SPEs due to room-temperature operation, strong second-order nonlinearity, and mature fabrication technology for photonic integrated circuits (PICs). Here, we report on deterministic creation of optically active defects in AlN toward monolithic integration of SPEs into AlN-on-sapphire PICs. In this work, we implant 7-Li+ ions in a periodic array into CVD AlN-on-sapphire with a pitch of 2 μm and 35 keV energy with ion fluences from 1x1016 - 1x1018 ions/cm2 by focused ion beam. To achieve high dose a large beam limiting aperture is chosen and we measure the spot size to be 50 nm. The implant regions exhibit fluorescence after a subsequent annealing at 950 °C for 30 min in Ar environment. PL optical spectra at room temperature show broad emission between 700 and 800 nm, which has longer wavelength than PL from He broad-beam implanted AlN film (< 700 nm) [1]. Both PL spectra can originate from a point defect within AlN bandgap such as anti-site nitrogen vacancy complex (NAlVN) and divacancy (VAlVN), according to density functional theory calculation [2] or may be from an Li-based defect. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D67.00004: Optical Amplification from Er Optical Center in GaN in the Visible region Jiarong R Cui, Ho X Vinh, Ngoc L.H. Hoang, Aidan Lentz, Nusrat Jahan, Vinh Q Nguyen Optical amplification from Rare-earth doped GaN semiconductor has been demonstrated in the visible region. We have reported a stronger emission and an optical amplification in GaN:Er materials synthesized by sputtering under the resonant excitation via the higher-lying inner 4f shell transitions and the band-to-band excitation of the GaN host. The observation of the optical amplification has been demonstrated through characteristic features of threshold behavior of emission intensity as a function of optical pump power. Employing the transient time-resolved photoluminescence technique, we have discovered the temperature independence of the photoluminescent decay dynamics for both isolated-Er and defect related optical centers in GaN. The optical amplification in GaN semiconductor opens up new possibilities for extended functionalities and integration capabilities for optoelectronic devices. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D67.00005: Understanding radiative emissions in the vicinity of selected-area regrown GaN diodes Sam Frisone, Alexander Chang, Sizhen Wang, Bingjun Li, Rachel S Goldman, Lincoln J Lauhon, Jung Han Selected-area growth (SAG) is a promising approach to achieve vertical p-n diodes for high power devices. However, leakage currents at vertical and lateral junctions often limit diode performance. Here we examine correlations between interfacial impurities and cathodoluminescence (CL) emission in SAG GaN trenches with and without Mg-doping. In all spectra, a 3.40 eV peak due to near band edge emission is observed. Most spectra also include a beam-energy dependent peak at 2.25 eV, termed yellow luminescence (YL). Since all interaction volumes include UID-GaN, YL is associated with VGa or its complexes with Si or C. For p-GaN trenches, emissions at 2.85 and 3.25 eV are observed near the trench edge and center, respectively. Interestingly, atom probe tomography reveals increased [O] at trench edges and secondary-ion mass spectroscopy reveals increased [Si] at planar regrowth interfaces. Thus, we attribute the 2.85 and 3.25 eV emissions to O-Mg donor-acceptor pair (DAP) and Si-Mg shallow-donor-acceptor pair (SDAP) emissions. These assignments are confirmed by a lack of DAP and SDAP emissions in spectra from UID-GaN trenches. We discuss the relationship between [Mg], the intensity of CL emission, and its implications for diode performance. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D67.00006: Temperature Dependence of Spectral Emission from GaN Defect Quantum Emitters Yifei Geng, Jialun Luo, Len H van Deurzen, Debdeep Jena, Gregory D Fuchs, Farhan Rana The study of quantum emitters in technologically mature wide bandgap semiconductors is attractive for photonic integration. We report results on single-photon defect emitters in MOVPE and MBE grown GaN epitaxial layers. Our experimental results show brightness levels for GaN emitters, with integrated solid immersion lenses, comparable to h-BN quantum emitters. GaN emitters display a strong zero phonon line (ZPL) even at room temperature. Interestingly, the temperature dependence of the emission linewidth does not follow a power law, as in the case of most defect emitters (SiC, NV diamond, etc), but exhibits an exponential temperature dependence from 50K to 300K, with a Lorentzian lineshape. The exponential temperature dependence and the corresponding Lorentzian lineshape can be described very well with our model that involves quadratic coupling of the emitter to optical phonons. Below 30K, the emission lineshape is Gaussian and the linewidth saturates at ~0.2 nm. The low temperature linewidth is dominated by spectral diffusion related to the built-in polarization fields in GaN. We will discuss the nature of the GaN defect emitters and the opportunities offered by defect quantum emitters in an optically active wide bandgap material system. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D67.00007: Understanding the zincblende to wurtzite polytype transition during epitaxy of gallium nitride nanowires Abby Liu, Hongling Lu, Rachel S Goldman Due to reduced strain-induced polarization in nanowires (NWs) and reduced spontaneous polarization for zincblende (ZB) polytypes, ZB GaN NWs are ideal candidates for high efficiency visible optoelectronics. To date, a predictive framework for selection of ZB vs. wurtzite (WZ) polytype NWs has yet to be established. Recently, we examined the influence of Ga supersaturation on polytype selection during molecular-beam epitaxy of GaN NW ensembles. Using real-time reflection high-energy diffraction, in combination with post-growth low-incident-beam-angle x-ray diffraction, we identified conditions for the nucleation of ZB NWs and films. We hypothesize that high Ga-flux during Ga pre-deposition hinders SixNy formation, allowing epitaxy of ZB GaN on silicon. Interestingly, ZB NWs and films transform to the WZ polytype after ~ 1 hour of growth. Therefore, the transformation is likely not due to a random event but instead likely due to heating at the growth surface, suggesting opportunities for tailoring the ZB-WZ polytype transformations. We will discuss investigations of individual NWs using high resolution transmission electron microscopy, in particular searching for the stacking faults in the vicinity of the ZB-WZ polytype transformation. |
Monday, March 14, 2022 4:48PM - 5:00PM |
D67.00008: A first principles study of n-doping of cubic boron nitride with carbon Cyrille Armel Sayou Ngomsi, Pratibha Dev Cubic boron nitride (cBN) is a super-hard, ultra-wide bandgap material that is being explored for extreme applications. To realize cBN-based devices, however, one needs to controllably n- and p-dope cBN, which has remained a challenge for this material. Recent progress in harnessing the full potential of cBN include: (i) an elucidation of reasons behind doping limitations in a comprehensive theoretical study [arXiv:2107.04454] and (ii) successful doping of cBN with carbon in experiment [ACS Applied Electronic Materials 3, 1359 (2021)]. However, the identity of the carbon-based shallow defect remains unknown. In the present theoretical work, we use density functional theory to investigate properties of carbon as a dopant, and the effects of different intrinsic and extrinsic defects that are often present in cBN. Our analysis reveals the possible candidate carbon-based defects with ionizable, delocalized (shallow) impurity states. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D67.00009: The Effect of Lattice Relaxation on Nitrogen Incorporation in GaAsN(Bi) Alloys Albert Tsui, Timothy Jen, Rachel S Goldman, Liang Qi Due to the significant band gap narrowing and complementary strain induced by dilute fractions of N and Bi in GaAs, dilute nitride-bismide alloys are of significant interest for near to mid-infrared applications. However, N-related point defects often lead to degraded minority carrier transport and reduced optical efficiencies. For dilute GaAsN alloys, ~20% of N shares an As site with either As or another N, termed (N-As)As or (N-N)As split interstitials.1 Using channeling-nuclear reaction analysis in combination with Monte-Carlo-Molecular Dynamics (MC-MD) simulations along the [100], [110], and [111] directions, (N-As)As was identified as the primary interstitial complex.2 However, the effect of lattice relaxation in the vicinity of incorporated N was not considered. Here, we use density functional theory to compute the relaxed structures of GaAs containing Nsub, (N-As)As, and (N-N)As, which are subsequently input into MC-MD simulations along the [100], [110], and [111] directions. We compare the computed yield trends with those measured for GaAsN and GaAsNBi alloys. |
Monday, March 14, 2022 5:12PM - 5:24PM |
D67.00010: Inversion Domain Boundaries in Wurzite GaN Mohamed Mauroof F Umar, Jorge O Sofo We introduce a convenient notation to distinguish $\{10\overline{1}0\}$-planar inversion domain boundary (IDB) models. Conventionally, the existing models for IDBs, Holt-IDB and IDB*, are distinguished based on the additional $1/2 \mathbf{c}$ relative shift between the domains in IDB*. We note the $1/2 \mathbf{c}$ relative shift in IDB* can be characterized as a misalignment of stacking planes on either side of the defect. Using this fact, in our notation the existing models for $\{10\overline{1}0\}$-planar IDBs are characterized by specifying the polarity and stacking plane alignments on either side of the defect plane. By considering all the possibilities for the stacking plane alignments on either side of the defect, we propose to new models for $\{10\overline{1}0\}$-planar IDBs. One of these new models, labelled IDB’, is energetically viable and its domain wall energy is lower than Holt-IDB. Even though IDB’ has a higher domain wall energy compared to IDB*, we argue that IDB’ may be formed in typical growth conditions. We present evidence from existing literature that confirms the existence of IDB’, however the defect plane has been misidentified as Holt-IDB. Additionally, when creating supercells containing domain walls, in order to calculate associated energies using plane wave density functional theory, certain domain walls disrupt the periodicity of the supercells. We propose an improved method to produce supercells containing these types of domain walls, thereby improving the estimations of these domain wall energies. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D67.00011: Recovery mechanism of reverse leakage current in GaN HEMTs following thermal storage test Jayjit Mukherjee, Rupesh K Chaubey, Dipendra S Rawal, Rajendra S Dhaka High leakage current in reverse bias is a widely reported reliability issue in AlGaN/GaN high electron mobility transistors (HEMTs). The material quality and the electric field at the gate terminal accounts for various tunnelling processes contributing to the observed leakage currents. In this study, the HEMTs were subjected to 573K (300OC) for 8 and 12 hrs and the reverse gate leakage current was observed at VGS = -8V and VDS = 5V throughout a period of 72 hrs. The gate current was modelled using phonon assisted tunnelling (PAT) and trap assisted tunnelling (TAT) components for a range of temperatures as well as after 72 hrs recovery from 573K. The extracted density of interface states (Dit) values (0.4 – 4.9 x 1014 cm-2) follow a monotonic trend with increasing temperatures showing increased PAT dominated current above a critical temperature (T > 500K). The presence of deep AlGaN barrier trap (1.18 eV) activates the TAT component as well as slows down the recovery through slow emission from the trap centres. This is experimentally found from the characteristic recovery time period around 5 - 13 hrs. The post recovery current values are observed to be one order higher than the pristine values suggesting a partial degradation in the devices due to the applied thermal stress. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700