Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P27: Semiconductors: Electrical Transport |
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Sponsoring Units: FIAP Chair: Ernesto Marinero, Perdue University Room: 290 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P27.00001: Resistivity of the insulating phase approaching the 2D metal-insulator transition: the effect of spin polarization Shiqi Li, Myriam Sarachik We compare the resistivity of the dilute, strongly-interacting 2D electron system in the insulating phase of a silicon MOSFET for unpolarized electrons in the absence of magnetic field and in the presence of an in-plane magnetic field sufficient to fully polarize the electrons. In both cases the resistivity obeys Efros-Shklovskii variable range hopping $\rho(T) = \rho_0 \mbox{exp}[(T_{ES}/T)^{1/2}]$, with $T_{ES}$ and $1/\rho_0$ mapping onto each other provided one applies a shift reported earlier of the critical density $n_c$ with magnetic field: the transport properties of the insulator are the same for unpolarized and fully polarized electron spins. Interestingly, the parameters $T_{ES}$ and $1/\rho_0 = \sigma_0$ are consistent with critical behavior approaching a metal-insulator transition. [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P27.00002: Abstract Withdrawn
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Wednesday, March 15, 2017 2:54PM - 3:06PM |
P27.00003: Weak localization and Shubnikov-de Haas oscillation in high carrier density AlInN/GaN heterostructures Lei Wang, Sakib Muhtadi, Ming Yin, Eun Sang Choi, Asif Khan, Timir Datta AlInN/GaN heterostructures are of interest due to the potential application in high power and high frequency electronic devices. Here we report on the electrical and magneto transport studies of high carrier density 2DEG in AlInN/GaN heterostructure from 2K to 280K for fields up to 18T. At low temperatures, Shubnikov-de Haas oscillation at high magnetic fields and weak localization at low fields are observed. From the temperature dependent amplitude of SdH oscillation and Dingle plot, the effective mass of electron is extracted as m*$=$0.2327me, and quantum scattering time 0.035ps. Consistent with weak localization, the conductivity increases with increasing magnetic field at low fields. We find electron-electron interaction is dominant below 20K. With the increasing temperature, the scattering changes from acoustic phonon to optical phonon scattering. Consequently, throughout the temperature range studied the carrier mobility decreases as the temperature increases. [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P27.00004: Nonradiative hot carrier capture cross section of defects in GaN from first principles Jun Jiang, Georgios D. Barmparis, Sokrates T. Pantelides, X.-G. Zhang Recent progress in first-principles calculations of multiphonon processes in solids [1,2] allows direct calculation of nonradiative hot-carrier capture cross sections of defects in semiconductors. We apply the computational method in [1] to electron and hole capture cross sections of defects in GaN. As formulated, the method contains zeroth-order matrix elements for the phonon-assisted electron (or hole) transition, whose contribution is expected to be larger than the contributions of the usual, first-order, electron-phonon coupling matrix elements [2]. The calculated cross sections are compared to the first-order results in [2] and to experiments. [1] Barmparis, Georgios D., et al. Physical Review B 92.21 (2015): 214111. [2] Alkauskas, A., et. al, Physical Review B, 90(7), 075202. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P27.00005: Microwave induced magnetoresistance oscillations under bichromatic excitation in AlGaAs/GaAs 2D electron system Binuka Gunawardana, Rasanga Samaraweera, Chathuranga Munasinghe, Han-Chun Liu, Christian Reichl, Werner Wegscheider, Ramesh Mani Microwave radiation induced magnetoresistance oscillations observed in 2D electronic systems have shown a variation in those oscillations with microwave parameters such as, for example, the microwave frequency, the microwave power,[1] and the microwave linear polarization angle[2]. Here, we examine microwave induced magnetoresistance oscillations under bichromatic microwaves, under a systematic change of the microwave power, with the aim to compare the power-variation of the monochromatic- and bichromatic- excitation induced oscillatory diagonal resistance (Rxx). We find a sub-linear variation of the diagonal resistance at the extrema with microwave power for both bichromatic and monochromatic cases, and report the observed evolution in oscillatory Rxx line shapes. [1] R. G. Mani et al., Nature, 420, 646 (2002) [2] Tianyu Ye, Han-Chun Liu, W. Wegscheider, and R. G. Mani, Phys. Rev. B~89, 155307 [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P27.00006: Investigation of the Effects of Temperature Cycling on Crystalline and Amorphous Germanium Telluride using Raman Spectroscopy A. Glen Birdwell, Leonard De La Cruz, Sami Hawasli, Frank J. Crowne, Tony G. Ivanov Raman Spectroscopy is a powerful method for investigating the intrinsic properties of electronic materials and device structures. The technique can provide atomic-level structural, chemical, electronic, and even topological information on scales comparable to the geometries of many electronic devices. In our laboratory, we routinely use Raman imaging for characterizing RF switches based on phase change materials such as Germanium Telluride (GeTe). In this presentation, we report on the effects that initial temperature-ramping cycles have on both crystalline and amorphous GeTe starting materials, and suggest how the observed materials evolution can be used to explain phenomena observed in the early switching cycles of our RF device structures. Power-handling studies on these electronic devices reveal that such information is fundamental to understanding variations in device operation and potential failure modes. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P27.00007: The impact of neutral impurity concentration on charge drift mobility in N-type Ge crystals Hao Mei, Guojian Wang, Gang Yang, Dongming Mei High-purity germanium crystals are being grown using the Czochralski technique at the University of South Dakota. The carrier concentration, mobility and resistivity are measured by Hall Effect system. We investigated the impact of neutral impurity concentration on charge drift mobility in N-type Ge crystals. Several samples with measured mobility lager than 35000 cm\textasciicircum 2/Vs from the grown crystals were used for this investigation. With the measured mobility and the ionized impurity concentration, we were able to calculate the neutral impurity concentration by the Matthiessen's rule. The correlations between the neutral impurity concentrations with the radius of the crystals were studied. We report that the concentration of neutral impurity constrains charge draft mobility for N-type high-purity germanium crystals and the non-uniform distribution of neutral impurity could result in an anisotropy of draft time distribution in a given germanium detector. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P27.00008: Electrical behaviors of high purity germanium crystals at low temperature Gang Yang, Kyler Teron Kooi, Guojian Wang, Hao Mei, Dongming Mei The electric behaviors of high purity germanium (HPGe) crystals at low temperature play an important role in determining the purity level of such materials used to fabricate radiation detectors. In the present work, the temperature dependence of electrical properties has been measured for the temperature range from 4.2$^{o}$K to 100$^{o}$K in two types of HPGe samples, polycrystalline crystals and single crystals, containing different impurity concentrations. The conductivity versus the inverted temperature curves for all of samples was divided into three distinctive temperature ranges: (a) high temperature where the conductivity increased to a maximum with decreasing temperature, (b) intermedium temperature where the conductivity decreased proportionally with decreasing temperature, and (c) low temperature where the conductivity continued decreasing slowly with decreasing temperature. It was also found that there was a turning point on the conductivity vs temperature curves for both types of samples. However, the turning points for them were significantly different: 30K for single crystal samples while 60K for polycrystalline samples. We report our measurements in this paper. We acknowledge financial support from DOE EPSCor Program and the state of the South Dakota governor's research center. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P27.00009: Hyperdoping Si with transition metals for infrared detection Jay Mathews, Yining Liu, Wenjie Yang, Quentin Hudspeth, Girish Malladi, Harry Efstathiadis, James Williams, Jeffrey Warrender Recent advances in the field of laser hyperdoping have produced a new class of materials that could lead the way to silicon-based, CMOS-compatible infrared detectors. Using the method of ion implantation followed by pulsed laser melting (II-PLM), silicon films with impurities at concentrations well above the solid solubility limit can be fabricated. Recent work has centered on using transition metals like Au or Ti as the impurity, as their deep level impurity states broaden into intermediate bands, thereby creating sub-band gap optical absorption. In this work, we report on efforts to develop the fabrication methods for realization of photodetectors from Si:Au and Si:Ti, including etching the materials and forming Ohmic contacts. We also explore the optical and electrical properties of fabricated Si:Au and Si:Ti photodetectors. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P27.00010: Effects of high optical injection levels in polycrystalline Si wafers on carrier transport Doneisha Steele, Andrey Semichaevsky High levels of carrier injection in polycrystalline Si may arise, for example, in solar cells under concentrated sunlight. Mechanisms for non-radiative carrier recombination include trap-mediated SRH and higher-order processes, e.g., Auger recombination [1]. In this paper we present our experimental results for intensity-dependent carrier lifetimes and conduction currents in polycrystalline Si wafers illuminated with pulses of up to 50 Sun intensity. We also use a computational model for carrier transport that includes both SRH and Auger recombination mechanisms, in order to explain our experiments. The model allows quantifying recombination rate dependence on carrier concentration. Our goal is to relate the recombination rates to Si microstructure and defect densities [2] that are revealed by IR PL images. We acknowledge the NSF support through grant 1505377. {[1] A. Richter, S.W. Glunz, F. Werner, J. Schmidt, and A. Cuevas, Improved quantitative description of Auger recombination in crystalline silicon, Phys. Rev. B 86, 165202 (2012).} [2] H. C. Sio, T. Trupke, D. Macdonald, Quantifying carrier recombination at grain boundaries in multicrystalline silicon wafers through photoluminescence imaging. J. Appl. Phys. 116, 244905 (2014). [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P27.00011: Dynamic Tuning of Charge Transport in Organometal Halide Perovskites Xi Wang, Yichuan Ling, Yu-Che Chiu, Yijun Du, Jorge Luis Barreda Esparza, Fernando Perez-Orive, Biwu Ma, Peng Xiong, Hanwei Gao Organometal Halide Perovskite has attracted a lot of attention for their potential in a variety of optoelectronic applications. Closely related to device functionalities and viability, the unusual behaviors such as current voltage hysteresis and switchable PV effect (poling to activation devices) are of particular interest. In this work, we studied microscopically the photoelectric responses of polycrystalline methylammonium lead halide (CH3NH3PbI3) thin films. The formation of dynamic p-n junctions and dissipation kinetics are observed in our devices. The dynamically formed electric field of p-n junctions can be effectively tuned by applying various external bias voltages. The experimental results agree well with the phenomena predicted using a model based on ion migration which give indication about the explanation of the external bias-induced rectified IV curves, IV hysteresis and the switchable PV effect observed in these materials. The results will provide insights into future designation of stable optoelectronic devices and dynamic p-n junction based devices using organometal halide perovskites. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P27.00012: Temperature Dependent Surface Structures and Electronic Properties of Organic-Inorganic Hybrid Perovskite Single Crystals M.-H. Jao, M. L. Teague, J.-S. Huang, W.-S. Tseng, N.-C. Yeh Organic-inorganic hybrid perovskites, arising from research of low-cost high performance photovoltaics, have become promising materials not only for solar cells but also for various optoelectronic and spintronic applications. An interesting aspect of the hybrid perovskites is that their material properties, such as the band gap, can be easily tuned by varying the composition, temperature, and the crystalline phases. Additionally, the surface structure is critically important for their optoelectronic applications. It is speculated that different crystalline facets could show different trap densities, thus resulting in microscopically inhomogeneous performance. Here we report direct studies of the surface structures and electronic properties of hybrid perovskite CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ single crystals by scanning tunneling microscopy and spectroscopy (STM/STS). We found long-range spatially homogeneous tunneling conductance spectra with a well-defined energy gap of (1.55 $\pm$ 0.1) eV at 300 K in the tetragonal phase, suggesting high quality of the single crystals. The energy gap increased to (1.81 $\pm$ 0.1) eV in the orthorhombic phase, below the tetragonal-to-orthorhombic phase transition temperature at \textasciitilde 150 K. Detailed studies of the temperature evolution in the spatially resolved surface structures and local density of states will be discussed to elucidate how these properties may influence the optoelectronic performance of the hybrid perovskites. [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P27.00013: Variation of the conductance enhancement at BaSnO$_{\mathrm{3}}$/LaIn$_{\mathrm{x}}$Ga$_{\mathrm{1-x}}$O$_{\mathrm{3}}$ polar Interface Young Mo Kim, Juyeon Shin, Youjung Kim, Kookrin Char We have recently reported that La-doped BaSnO$_{\mathrm{3}}$ (BLSO) displayed conductance enhancement by more than 10$^{\mathrm{4}}$ times when LaInO$_{\mathrm{3}}$ (LIO) layer was grown on top of the BLSO layer. The conductance enhancement implies the two-dimensional electron gas (2DEG) formation at the interface. To identify the origin of the conductance enhancement, we developed other heterostructures based on different overlayers. Since LaGaO$_{\mathrm{3}}$ is also a polar perovskite like the LIO with its band gap of 4.4 eV and its lattice constant of 3.9 Å, we investigated the variation of the conductance enhancement at LaIn$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$O$_{\mathrm{3}}$ (LIGO)/BLSO interface while varying the Ga ratio. We first checked the interfacial epitaxial growth of LIGO on BSO by x-ray diffraction measurement and transmission electron microscopy. The sheet conductances of BLSO layer before and after the deposition of LIGO layer were measured. Putting together the structural and electrical properties of the LIGO/BLSO interfaces with various Ga compositions, we will discuss the origin of the conductance enhancement in terms of the strain-induced polarization in the LIGO layer. [Preview Abstract] |
Wednesday, March 15, 2017 5:06PM - 5:18PM |
P27.00014: Abstract Withdrawn
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Wednesday, March 15, 2017 5:18PM - 5:30PM |
P27.00015: Abstract Withdrawn |
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