Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session E54: Microwave and Optical Properties of SemiconductorsIndustry
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Sponsoring Units: FIAP Chair: Todd Brintlinger, Naval Research Lab Room: Hilton Baltimore Holiday Ballroom 5 |
Tuesday, March 15, 2016 8:00AM - 8:12AM |
E54.00001: Study of microwave reflection in the regime of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs 2D electron system Annika Kriisa, H-C. Liu, R. L. Samaraweera, M. S. Heimbeck, H. O. Everitt, W. Wegscheider, R. G. Mani Microwave-induced zero-resistance-states in the photo-excited GaAs/AlGaAs system evolve from the minima of microwave photo-excited “quarter-cycle shifted” magnetoresistance oscillations. Such magnetoresistance oscillations are known to exhibit nodes at cyclotron resonance ($hf = \hbar \omega_c$) and cyclotron resonance harmonics ($hf = n\hbar \omega_c$). Further, the effective mass extracted from the radiation-induced magnetoresistance oscillations is known to differ from the canonical effective mass ratio for electrons in the GaAs/AlGaAs system.[1] In an effort to reconcile this difference, we have looked for cyclotron resonance in the microwave reflection from the high mobility 2DES and attempted to correlate the observations with observed oscillatory magnetoresistance over the $30 \le f \le 330$ GHz band. The results of such a study will be reported here. [1] R. G. Mani et al., Phys. Rev. Lett. 92, 146801 (2004). [Preview Abstract] |
Tuesday, March 15, 2016 8:12AM - 8:24AM |
E54.00002: Frequency-dependence of the linear-polarization-angle phase-shift in the microwave radiation-induced magnetoresistance oscillations Han-Chun Liu, Rasanga Samaraweera, Werner Wegscheider, Ramesh Mani High-mobility GaAs/AlGaAs heterojunctions subjected to microwave photoexcitation in the perpendicular magnetic field configuration exhibit \textonequarter -cycle phase-shifted oscillatory magnetoresistance and zero-resistance states at low magnetic fields or high filling factors [1]. Recent studies showed that the amplitude of oscillatory magnetoresistance is polarization-angle sensitive and can be described by a fitting formula, Rxx($\theta )=$A\textpm Ccos2($\theta $-$\theta $0) with diagonal resistance, Rxx, polarization angle $\theta $, and the extracted phase shift, $\theta $0. Previous works have demonstrated that $\theta $0 is frequency-dependent by investigating some specific frequencies [2,3]. Here, we examine the continuous variation of $\theta $0 with frequency over the bands, 36-40 GHz and 45-49 GHz. Surprisingly, the results indicate dissimilar $\theta $0 variation within the two frequency bands. A comparison of $\theta $0(f) with the microwave polarization reported by an in-situ polarization sensor suggests that the frequency variation of $\theta $0 might be caused by two different mechanisms in the two examined bands. [1] R. G. Mani et al., Nature 420, 646 (2002). [2] A. N. Ramanayaka et al., Phys. Rev. B 85, 205315 (2012). [3] Han-Chun Liu et al., J. Appl. Phys. 117, 064306 (2015) [Preview Abstract] |
Tuesday, March 15, 2016 8:24AM - 8:36AM |
E54.00003: Microwave radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs system under bichromatic excitation Binuka Gunawardana, Han-Chun Liu, Rasanaga Samaraweera, Werner Wegscheider, Ramesh Mani Bichromatic microwave excitation has been used in atomic physics, for example, to destabilize the populations distribution of cold atoms.[1] In semiconductor physics, bichromatic excitation of the high mobility 2D electron system is thought to provide evidence for current domains in the regime of the microwave radiation-induced zero-resistance states[2-4]. We examined radiation-induced magneto-resistance oscillations under bichromatic excitation over the 30 \textless f \textless 100 GHz band to obtain a better understanding of the lineshape observed in the dual excitation experiment of the high mobility GaAs/AlGaAs 2D electron system. Thus, we photo-excited the GaAs/AlGaAs Hall bar specimen at liquid helium with one microwave source at a fixed, relatively high frequency and a second microwave source at several lower frequencies corresponding to various frequency ratios. The microwave intensity due to both sources were also changed systematically to study the evolution of the oscillatory magnetoresistance lineshape. Here, we report the results of this study which aims to examine superposition- or lack thereof- in the lineshape observed in the bichromatic experiment. [1]A. Buchleitner,~L. Sirko~and~H. Walther Europhysics Lett. 16, 35 (1991). [2] R. G. Mani et al., Nature, 420, 646 (2002) [3] M. A. Zudov et al., Phys. Rev. Lett. 96, 236804 (2004). [4] X. L. Lei and S. Y. Liu, Appl. Phys. Lett. 89, 182117 (2006). [Preview Abstract] |
Tuesday, March 15, 2016 8:36AM - 8:48AM |
E54.00004: Analysis of bell-shape negative giant-magnetoresistance in high mobility GaAs/AlGaAs 2D electron systems using multi-conduction model. Rasanga Samaraweera, Han-Chun Liu, Werner Wegscheider, Ramesh Mani Recent advancements in the growth techniques of the GaAs/AlGaAs two dimensional electron system (2DES) routinely yield high quality heterostructures with enhanced physical and electrical properties, including devices with 2D electron mobilities well above 10$^{7}$ cm$^{2}$/Vs. These improvements have opened new pathways to study interesting physical phenomena associated with the 2D electron system. Negative giant-magnetoresistance (GMR) is one such phenomenon which can observed in the high mobility 2DES. However, the negative GMR in the GaAs/AlGaAs 2DES is still not fully understood. In this contribution, we present an experimental study of the bell-shape negative GMR in high mobility GaAs/AlGaAs devices and quantitatively analyze the results utilizing the multi-conduction model [1]. The multi-conduction model includes interesting physical characteristics such as negative diagonal conductivity, non-vanishing off-diagonal conductivity, etc. The aim of the study is to examine GMR over a wider experimental parameter space and determine whether the multi-conduction model serves to describe the experimental results. [1] R. G. Mani, A. Kriisa, and W. Wegscheider, Sci. Rep. 3, 2747 (2013). [Preview Abstract] |
Tuesday, March 15, 2016 8:48AM - 9:00AM |
E54.00005: Microwave polarization angle study of the radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2D electron system under dc current bias Muhammad-Zahir Iqbal, Han-Chun Liu, Martin S. Heimbeck, Henry O. Everitt, Werner Wegscheider, Ramesh G. Mani Microwave-induced magnetoresistance oscillations followed by the vanishing resistance states are a prime representation of non-equilibrium transport phenomena in two-dimensional electron systems (2DES). The effect of a dc current bias on the nonlinear response of 2DES with microwave polarization angle under magnetic field is a subject of interest. Here, we have studied the effect of various dc current bias on microwave radiation-induced magnetoresistance oscillations in a high mobility 2DES. Further, we systematically investigate the effect of the microwave polarization angle on the magneto-resistance oscillations at two different frequencies 152.78 GHz and 185.76 GHz. This study aims to better understand the effects of both dc current and microwave polarization angle in the GaAs/AlGaAs system, both of which modify the observed magneto-transport properties [Preview Abstract] |
Tuesday, March 15, 2016 9:00AM - 9:12AM |
E54.00006: Microwave Reflection Spectroscopy of a Two-Dimensional Electron Gas Jie Zhang, Ruiyuan Liu, Lingjie Du, Rui-Rui Du, Loren Pfeiffer, Ken West Cyclotron resonance (CR) is a standard method to determine the carrier effective mass in two-dimensional electron systems, typically by measuring/analyzing the absorption or transmission signal. Here we report a microwave spectrometer utilizing the reflection signal. In our experiment setup based on a top-loading helium3 cryostat and a superconducting solenoid, the microwave (up to 40GHz)~ is sent down via a coax cable to the sample surface, and the reflection signal is then collected by the same cable and fed upward to a directional coupler, and being detected. We demonstrate the applicability of the spectrometer by measuring the CR of high-mobility electrons or holes in GaAs/AlGaAs quantum wells. The construction of spectrometer, preliminary data, and brief discussions will be presented. The work at Rice was supported by Welch Foundation grant C-1682. [Preview Abstract] |
Tuesday, March 15, 2016 9:12AM - 9:24AM |
E54.00007: Response of Plasmonic Terahertz Detectors to Modulated Signals Sergey Rudin, Greg Rupper, Meredith Reed, Michael Shur We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. Our model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor. The modulation response was evaluated as a function of modulation frequency for a range of mobility values in different semiconductor materials. Maximum modulation frequency was evaluated as a function of channel mobility, with typical values in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime meets the requirements for applications as terahertz detectors and modulators in high-speed wireless communication circuits. [Preview Abstract] |
Tuesday, March 15, 2016 9:24AM - 9:36AM |
E54.00008: Infrared magneto-transmission studies of the 2DEGs in (CdMn)Te and CdTe Quantum wells Imtiaz Tanveer, Maciej Wiater, Grzegorz Karczewski, Tomasz Wojtowicz, B.D. McCombe We are probing quantum hall ferromagnetism (QHF) in the 2DEG of Modulation-doped quantum wells (QWs) in the (CdMn)Te/(CdMg)Te (with 1.5\% Mn) heterostructure system by THz cyclotron resonance. Samples with CdTe QWs are also studied. Both structures have the same QW width (30 nm), very similar electron densities in the wells $\sim$3.0 x 10$^{11}$ cm$^{-2} $ and mobilities of 450,000 (CdTe) and 66,000 cm$^{2}$/Vs ((CdMn)Te) at 1.6 K. The electron effective masses (m*/m$ _{0} $) from cyclotron resonance measurements at 5K are 0.110 $\pm$ 0.001 for CdTe and 0.114 $\pm$ 0.003 for (CdMn)Te . Linear fits to the resonance positions in frequency vs.\ field give small non-zero intercepts which may result from small non-parabolicity or bound magneto-plasmon effects. The FWHM linewidths from Lorentzian fits of the transmission minima are $\sim$2 cm$ ^{-1} $(CdTe) and $\sim$8 cm$^{-1}$((CdMn)Te). Our present focus is on detailed studies of the CR positions and linewidths in the magnetic field region around the cusp-like behavior in the R$ _{xx} $ oscillations, which indicates the presence of the QHF state. The field position of this state is tuned via electron density in the QWs varied incrementally by a photon-dose method with an in-situ green LED. [Preview Abstract] |
Tuesday, March 15, 2016 9:36AM - 9:48AM |
E54.00009: Coherent coupling of magneto-excitons probed by two-dimensional Fourier transform spectroscopy Jagannath Paul, Cunming Liu, Stephen McGill, David Hilton, Denis Karaiskaj We present the coherent two dimensional Fourier Transform (2DFT) spectra of magneto-excitons in undoped GaAs quantum wells at high magnetic field up to 10 Tesla. The 2DFT data reveal strong coherent coupling between resonances and line shapes which are strikingly different from the zero field spectra. 2DFT spectra measured using co-linear and co-circular polarizations at low temperatures will be discussed. [Preview Abstract] |
Tuesday, March 15, 2016 9:48AM - 10:00AM |
E54.00010: Observation of a Bound Exciton Transition in Ion-Beam Synthesized $\beta $-FeSi$_{2}$ A. Glen Birdwell, Frank J. Crowne, Terrance P. O'Regan Photoreflectance studies of $\beta $-FeSi$_{2}$ have revealed the presences of strong (direct) optical transitions together with several interesting lower-energy spectral features, including indirect gap excitonic transitions. In this presentation, we focus on one of these features made observable at low temperatures and located a few meV below the first direct gap. We attribute the origin of this feature to a transition that takes place on a bound exciton-ionized acceptor complex. Our observations of this transition together with results of our previous photoreflectance analysis lead us to identify it as the fundamental mechanism for the 1.5 $\mu $m light emission in $\beta $-FeSi$_{2}$. This result provides deeper insight into the light emission properties of $\beta $-FeSi$_{2}$. [Preview Abstract] |
Tuesday, March 15, 2016 10:00AM - 10:12AM |
E54.00011: Langevin Bimolecular Recombination Kinetics of a Layered Exciton--Trion Gas Frank Crowne, Anthony Birdwell The use of rate equations to describe various many-body kinetic processes in highly photoexcited layered semiconductors is discussed. In these systems, pairs of electrons and holes generated by photons from an external laser combine to form a multicomponent plasma whose time evolution is governed by gas dynamics and various recombination processes. At high levels of illumination this leads to a variety of secondary components in addition to neutral excitons, notably the so-called trions, which consist of exciton--electron and exciton--hole bound states. Although the recombination is modeled as bimolecular for all pairs of carrier species, the structure of the rate terms is sensitive to the dimensionality of the system due to the Langevin nature of encounters between carriers. It is demonstrated that charge neutrality does not apply to individual carrier species, e.g., electron and hole densities need not be equal in the presence of trions. In order to track the full time evolution from laser initiation to steady state, the system of rate equations is simulated numerically. [Preview Abstract] |
Tuesday, March 15, 2016 10:12AM - 10:24AM |
E54.00012: Magneto-transport properties of PbSe single crystals Naween Anand, Catalin Martin, Genda Gu, David Tanner PbSe is a low-gap semiconductor with excellent infrared photodetection properties. Here we report our high magnetic field and low temperature electrical properties measurement performed on a moderately doped PbSe single crystals with p-type bulk carrier density of around 1\texttimes 10$^{18}$ cm$^{-3}$. Longitudinal resistance (R$_{xx})$ and Hall resistance (R$_{xy})$ were simultaneously measured between 0 T and 18 T, and at temperatures between 0.8 K and 25 K, show quantum oscillations above 6 T. The quantum oscillation frequency is \textasciitilde 15 T, giving an estimate for the carrier density of each L pocket in the BZ participating in these oscillations. The effective mass of the free carriers is estimated from the temperature dependence of oscillation amplitudes. Measurements as the magnetic fields is rotated reveal the magneto-transport properties of a 3D-like fermi surface. Dingle temperature and free carrier scattering rate has been estimated and compared to optical measurements. Optical measurements also show a low frequency phonon mode around 45 cm$^{-1}$ and bandgap of around 0.2 eV along with other interband electronic transitions. [Preview Abstract] |
Tuesday, March 15, 2016 10:24AM - 10:36AM |
E54.00013: Collosal figure of merit of transparent conducting nano-ribbon networks Jinwei Gao, Qiang Peng, Songru Li, Bing Han, Qikun Rong, Xubing Lu, Guofu Zhou, Jun-Ming Liu, Qianming Wang, Zhifeng Ren, Krzysztof Kempa An inexpensive, simultaneously transparent and conducting metallic nano-ribbon network can be obtained by exploiting the self-cracking property of the egg-white film, subsequently used as a sacrificial mask for metal sputtering. The process results in a network of metallic nano-ribbons ideally suited for electroplating. Due to large inter-ribon distance, an even 100-fold increase in the ribbon thickness has a negligible effect on the network transparency. Here we demonstrate this effect by developing a network with a colossal, by far the highest reported figure of merit of over 25000. This network can be used as an ultimate window electrode for solar cells, as well as LEDs. [Preview Abstract] |
Tuesday, March 15, 2016 10:36AM - 10:48AM |
E54.00014: Gate Tunable InSb Quantum Well Structures grown on GaSb (001) Mihir Pendharkar, Anthony McFadden, Borzoyeh Shojaei, Joon Sue Lee, Chris Palmstrom Study of quantum well structures with InSb channels is of special interest to the field of spintronics and quantum computing due to the strong spin orbit coupling and large g-factor of InSb. Gate control of InSb quantum wells is a necessary component in construction of an InSb based Spin-Field Effect Transistor. In this work, InSb quantum well structures have been grown on lattice mismatched GaSb substrates by Molecular Beam Epitaxy. Magneto-transport measurements at low temperatures have been used to investigate the influence of gate voltage on electron mobility and density. A conventional metal top gate, separated from the III-V structure with an Atomic Layer Deposited insulating dielectric, has been used. Use of the conducting GaSb substrate as a potential, bottom gate electrode has also been investigated. Surface morphology of as-grown films has been studied using Atomic Force Microscopy. [Preview Abstract] |
Tuesday, March 15, 2016 10:48AM - 11:00AM |
E54.00015: Reconciling Particle-Beam and Optical Stopping-Power Measurements in Silicon William Karstens, E. J. Shiles, David Y Smith A swift, charged particle passing through matter loses energy to electronic excitations \textit{via} the electro-magnetic transients experienced by atoms along its path. Bethe related this process to the matter's frequency-dependent dielectric function $\varepsilon (\hbar \omega )$ through the energy-loss function, Im[-1/$\varepsilon (\hbar \omega )$]. The matter's response may be summarized by a single parameter, the mean excitation energy, or $I$ value, that combines the optical excitation spectrum and excitation probability. Formally, ln $I$ is the mean of ln $\hbar \omega $ weighted by the energy-loss function. This provides an independent optical check on particle energy-loss experiments. However, a persistent disagreement is found for silicon: direct particle-beam studies yield 173.5\textless $I$\textless 176 eV, but a fit to the stopping-power of 36 elements suggests 165 eV. An independent determination from optical data in 1986 gave 174 eV supporting the higher values. However, recent x-ray measurements disclosed short comings in the 1986 optical data: 1. Measurements by Ershov and Lukirskii underestimated the L-edge strength, and 2. A power-law extrapolation overestimated the K-edge strength. We have updated these data and find $I=$ 162 eV, suggesting that silicon's recommended $I$ value should be reconsidered. While this 5{\%} change in $I$ value changes the stopping power by only 1{\%}, it is significant for precision measurements with Si detectors. [Preview Abstract] |
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