Electronic Devices and Semiconductor Manufacturing Commons^™

Performance Of Thin Film Ferroelectrics With Dopant-Ion Charges, Huadong Li, Guru Subramanyam, Jiadong Wang

Guru Subramanyam

This paper studied the effect of dopant-ion charges on the performance of thin film ferroelectrics. Field distributions and capacitance of ferroelectric thin films with different dopant-ion charge densities are analyzed. The non-linearity of the electric field inside the thin film increases with the dopant-ion charge density and decreases with the linear permittivity of the ferroelectric thin film. Once the applied voltage is strong enough, the field distribution will become linear. The FE thin film peak capacitance reduces with the dopant-ion charge density and the total area under the C-V curve between two large voltages with opposite signs is fixed.

Voltage Tunable Epitaxial Pb X Sr(1− X )Tio3 Films On Sapphire By Mocvd: Nanostructure And Microwave Properties, S. Dey, C. Wang, W. Cao, S. Bhaskar, J. Li, Guru Subramanyam

Guru Subramanyam

Frequency and phase agile microwave components such as tunable filters and phase shifters will require ferroelectric thin films that exhibit a nonlinear dependence of dielectric permittivity (ɛ _r ) with dc electric bias, as well as a high material (Δɛ _r /tan δ) and device (or K-factor in phase shift/dB) figure of merits (FOM). Therefore, voltage tunable (Pb_0.3Sr_0.7)TiO₃ (PST) thin films (90–150 nm) on (0001) sapphire were deposited by metal-organic chemical vapor deposition at rates of 10–15 nm/min. The as-deposited epitaxial PST films were characterized by Rutherford backscattering spectroscopy, X-ray methods, field …

Feature Extraction Of Rich Texture Document, Innovative Research Publications Irp India, Prajwalita Satish Ravan, Shrinivas A. Patil, Swapnil V. Vanmore

Innovative Research Publications IRP India

We describe here an efficient algorithm for reassembling one or more unknown objects that have been broken or torn into a large number N of irregular fragments. The puzzle assembly problem has many application areas such as restoration and reconstruction of archeological findings, repairing of broken objects, solving jigsaw type puzzles, molecular docking problem, etc. The pieces usually include not only geometrical shape information but also visual information such as texture, color, and continuity of lines. This paper presents a new approach to the puzzle assembly problem that is based on using textural features and geometrical constraints. The texture of …

Very-Low-Specific-Resistance Pd/Ag/Au/Ti/Au Alloyed Ohmic Contact To P Gan For High-Current Devices, V. Adivarahan, A. Lunev, M. Asif Khan, J. Yang, Grigory Simin, M. S. Shur, R. Gaska

Grigory Simin

We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to pGaN. An 800 °C anneal for 1 min in flowing nitrogen ambient produces an excellent ohmic contact with a specific contact resistivity close to 1×10−6 Ω cm2 and with good stability under high current operation conditions. This high-temperature anneal forms an alloy between Ag,Au, and pGaN resulting in a highly p-doped region at the interface. Using x-ray photoelectron spectroscopy and x-ray diffractionanalysis, we confirm that the contact formation mechanism is the metal intermixing and alloying with the semiconductor.

Algan/Gan Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors On Sic Substrates, M. Asif Khan, X. Hu, A. Tarakji, Grigory Simin, J. Yang, R. Gaska, M. S. Shur

Grigory Simin

We report on AlGaN/GaN metal–oxide–semiconductor heterostructurefield-effect transistors (MOS-HFETs) grown over insulating 4H–SiC substrates. We demonstrate that the dc and microwave performance of the MOS-HFETs is superior to that of conventional AlGaN/GaN HFETs, which points to the high quality of SiO2/AlGaNheterointerface. The MOS-HFETs could operate at positive gate biases as high as +10 V that doubles the channel current as compared to conventional AlGaN/GaN HFETs of a similar design. The gate leakage current was more than six orders of magnitude smaller than that for the conventional AlGaN/GaN HFETs. The MOS-HFETs exhibited stable operation at elevated temperatures up to 300 °Cwith excellent …

Mechanism Of Radio-Frequency Current Collapse In Gan-Algan Field-Effect Transistors, A. Tarakji, Grigory Simin, N. Ilinskaya, X. Hu, A. Kumar, A. Koudymov, J. Yang, M. Asif Khan, M. S. Shur, R. Gaska

Grigory Simin

The mechanism of radio-frequency current collapse in GaN–AlGaN heterojunctionfield-effect transistors(HFETs) was investigated using a comparative study of HFET and metal–oxide–semiconductor HFET current–voltage (I–V) and transfer characteristics under dc and short-pulsed voltage biasing. Significant current collapse occurs when the gate voltage is pulsed, whereas under drain pulsing the I–V curves are close to those in steady-state conditions. Contrary to previous reports, we conclude that the transverse electric field across the wide-band-gap barrier layer separating the gate and the channel rather than the gate or surface leakage currents or high-field effects in the gate–drain spacing is responsible for the current collapse. We …

Low Clutter Method For Bistatic Rcs Measurements, Peter J. Collins

AFIT Patents

A bistatic radar measurement system is provided having a radar source configured to produce a radio frequency signal. A transmitting antenna is configured to transmit the radio frequency signal toward a target. A receiving antenna is configured to receive a reflected radio frequency signal from the target. A support system is configured to support the receiving antenna. The support system includes a plurality of low scattering dielectric strings configured to orient the receiving antenna.

Electronic Desalting For Controlling The Ionic Environment In Droplet-Based Biosensing Platforms, Vikhram Vilasur Swaminathan, Piyush Dak, Bobby Reddy Jr, Eric Salm, Carlos Duarte-Guevara, Yu Zhong, Andrew Fischer, Yi-Shao Liu, Rashid Bashir

Birck and NCN Publications

The ability to control the ionic environment in saline waters and aqueous electrolytes is useful for desalination as well as electronic biosensing. We demonstrate a method of electronic desalting at micro-scale through on-chip micro electrodes. We show that, while desalting is limited in bulk solutions with unlimited availability of salts, significant desalting of ≥1 mM solutions can be achieved in sub-nanoliter volume droplets with diameters of ∼250 μm. Within these droplets, by using platinum-black microelectrodes and electrochemical surface treatments, we can enhance the electrode surface area to achieve >99% and 41% salt removal in 1 mM and 10 mM salt …

Variable Attenuator Blends Dynamic Range, Linearity, Chin-Leong Lim

Chin-Leong Lim

A voltage variable attenuators (VVA) with compact dimensions and high linearity can be realized by connecting PIN diodes in the form of a π network. However this VVA's maximum frequency is limited to ~1 GHz because of signal leakage through the series diodes' parasitic capacitances. The ceiling frequency can significantly raised by resonating the parasitic capacitance with a parallel inductor. This technique has been previously demonstrated on a discrete design. To reduce component count and size, this work extends the technique to a standalone, highly-integrated module. This paper reports the performances achieved at 3.5 GHz.

The prototype's attenuation is adjustable …

Challenges And Opportunities For Multi-Functional Oxide Thin Films For Voltage Tunable Radio-Frequency/Microwave Components, Guru Subramanyam, M W. Cole, Nian X. Sun, Thottam S. Kalkur, Nick M. Sbrockey, Gary S. Tompa, Xiaomei Guo, Chonglin Chen, S P. Alpay, G A. Rossetti Jr., Kaushik Dayal, Long-Qing Chen, Darrell G. Schlom

Guru Subramanyam

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated …

Trapping Light With Nanostructures For Sensors, Kareem Garriga

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Strain Controlled Ultra-Low-Energy Magnetic Tunneling Junction, Hasnain Ahmad, Supriyo Bandyopadhyay, Jayasimha Atulasimha

Graduate Research Posters

We are experimenting on designing a voltage-controlled ultra-low-energy Magnetic Tunneling Junction (MTJ) device using a soft single domain magnetostrictive layer (i.e. Galfenol: Fe_1-xGa_x , x = 20 At%) coupled to a piezoelectric layer (i.e. PMN-PT). Special metal pads have been designed using photolithography to generate stress in the PMN-PT layer by applying electric field. The patterns of different shape anisotropic nano-magnets are designed using e-beam lithography and we have successfully fabricate FeGa nanomagnets with only 12 to 13 nanometer thickness by sputter deposition. These nanomagnets have been characterized by magnetic force microscopy for observing their switching capabilities. …

Bifacial Si Heterojunction-Perovskite Organic-Inorganic Tandem To Produce Highly Efficient (Η T * ~ 33%) Solar Cell, Reza Asadpour, Raghu Vamsi Krishna Chavali, Mohammad Ryyan Khan, Muhammad Ashraful Alam

Department of Electrical and Computer Engineering Faculty Publications

As single junction photovoltaic (PV) technologies both Si heterojunction (HIT) and perovskite based solar cells promise high efficiencies at low cost. Intuitively a traditional tandem cell design with these cells connected in series is expected to improve the efficiency further. Using a self-consistent numerical modeling of optical and transport characteristics however we find that a traditional series connected tandem design suffers from low JSC due to band-gap mismatch and current matching constraints. Specifically a traditional tandem cell with state-of-the-art HIT ( η=24% ) and perovskite ( η=20% ) sub-cells provides only a modest tandem efficiency of η_T~ 25%. …

Multiferroic Tunnel Junctions And Ferroelectric Control Of Magnetic State At Interface, Y. W. Yin, M. Raju, W. J. Hu, John D. Burton, Y.-M. Kim, A. Y. Borisevich, S. J. Pennycook, S. M. Yang, T. W. Noh, Alexei Gruverman, X. G. Li, Z. D. Zhang, Evgeny Y. Tsymbal, Qi Li

Alexei Gruverman Publications

As semiconductor devices reach ever smaller dimensions, the challenge of power dissipation and quantum effect place a serious limit on the future device scaling. Recently, a multiferroic tunnel junction (MFTJ) with a ferroelectric barrier sandwiched between two ferromagnetic electrodes has drawn enormous interest due to its potential applications not only in multi-level data storage but also in electric field controlled spintronics and nanoferronics. Here, we present our investigations on four-level resistance states, giant tunneling electroresistance (TER) due to interfacial magnetoelectric coupling, and ferroelectric control of spin polarized tunneling in MFTJs. Coexistence of large tunneling magnetoresistance and TER has been observed …

Investigation Of Gate Dielectric Materials And Dielectric/Silicon Interfaces For Metal Oxide Semiconductor Devices, Lei Han

Theses and Dissertations--Electrical and Computer Engineering

The progress of the silicon-based complementary-metal-oxide-semiconductor (CMOS) technology is mainly contributed to the scaling of the individual component. After decades of development, the scaling trend is approaching to its limitation, and there is urgent needs for the innovations of the materials and structures of the MOS devices, in order to postpone the end of the scaling. Atomic layer deposition (ALD) provides precise control of the deposited thin film at the atomic scale, and has wide application not only in the MOS technology, but also in other nanostructures. In this dissertation, I study rapid thermal processing (RTP) treatment of thermally grown …

Nanostructured Semiconductor Device Design In Solar Cells, Hongmei Dang

Theses and Dissertations--Electrical and Computer Engineering

We demonstrate the use of embedded CdS nanowires in improving spectral transmission loss and the low mechanical and electrical robustness of planar CdS window layer and thus enhancing the quantum efficiency and the reliability of the CdS-CdTe solar cells. CdS nanowire window layer enables light transmission gain at 300nm-550nm. A nearly ideal spectral response of quantum efficiency at a wide spectrum range provides an evidence for improving light transmission in the window layer and enhancing absorption and carrier generation in absorber. Nanowire CdS/CdTe solar cells with Cu/graphite/silver paste as back contacts, on SnO₂/ITO-soda lime glass substrates, yield the …

Limiters Protect Adcs Without Adding Harmonics, Chin-Leong Lim

Chin-Leong Lim

High-speed Analogue to Digital Converters (ADC) are used for sampling at either the intermediate frequency (IF) or the radio frequency of wireless receivers. When the transmitter is nearby, the sampled signal can exceed the ADC’s maximum input level. So, amplitude limiting is necessary to prevent ADC damage or degradation. While automatic gain control is effective for controlling IF amplitude excursion in traditional single-carrier systems, it is not desirable in modern multi-carrier applications. One solution is to cap the IF amplitude excursion with a limiter. Unfortunately, a new problem is created – the strong non-linearity that is required of a good …