Modeling Electrical Resistance Drift with Ultrafast Saturation of OTS Selectors

Crossbar array architecture is an essential design element for densely connected Non-Volatile Memory(NVM) applications. To overcome intrinsic sneak current problem of crossbar arrays, each memory unit is serially attached to a selector unit with highly nonlinear current-voltage (I-V) characteristics. Recently, Ovonic Threshold Switching (OTS) materials are preferred as selectors due to their fabrication compatibility with PRAM, MRAM or ReRAM technologies; however, OTS selectors suffer from the temporal drift of its threshold voltage. First, based on Poole-Frenkel conduction, we present time and temperature dependent model that predicts temporally evolving I-V characteristics,including threshold voltage of OTS selectors. Second, we report an ultrafast saturation (∼103 seconds) of the drift and extend the model to predict the time of drift saturation. Our model shows excellent agreement with OTS devices fabricated with 8 nm technology node at 25°C and 85°C ambient temperatures. The proposed model plays a significant role in understanding OTS device internals and the development of reliable threshold voltage jump table

Modeling Electrical Resistance Drift with Ultrafast Saturation of OTS Selectors

Crossbar array architecture is an essential design element for densely connected Non-Volatile Memory(NVM) applications. To overcome intrinsic sneak current problem of crossbar arrays, each memory unit is serially attached to a selector unit with highly nonlinear current-voltage (I-V) characteristics. Recently, Ovonic Threshold Switching (OTS) materials are preferred as selectors due to their fabrication compatibility with PRAM, MRAM or ReRAM technologies; however, OTS selectors suffer from the temporal drift of its threshold voltage. First, based on Poole-Frenkel conduction, we present time and temperature dependent model that predicts temporally evolving I-V characteristics,including threshold voltage of OTS selectors. Second, we report an ultrafast saturation ($\sim 10^3$ seconds) of the drift and extend the model to predict the time of drift saturation. Our model shows excellent agreement with OTS devices fabricated with 8 nm technology node at 25{\deg}C and 85{\deg}C ambient temperatures. The proposed model plays a significant role in understanding OTS device internals and the development of reliable threshold voltage jump table

Scattering of Spin-12\frac{1}{2} Particles from a PT\cal PT-symmetric Complex Potential

In this letter, we study the scattering of spin-$\frac{1}{2}$ particles from a spin-independent parity time ($\cal PT$)-symmetric complex potential, and for the first time, theoretically demonstrate the coexistence of $\cal PT$-symmetric and $\cal PT$-broken phases for broadband energy spectra in this system. We also show the existence of anisotropic transmission resonances, accessible through the tuning of energy. Our results are promising for applications in spintronics, semiconductor-based devices, and a better understanding of the topological surface states.Comment: 6 pages, 4 figures, 1 tabl

Forward tunneling current in Pt/p-InGaN and Pt/n-InGaN Schottky barriers in a wide temperature range

a b s t r a c t The current-transport mechanisms of the Pt contacts on p-InGaN and n-InGaN were investigated in a wide temperature range (80-360 K) and in the forward bias regime. It was found that the ideality factor (n) values and Schottky barrier heights (SBHs), as determined by thermionic emission (TE), were a strong function of temperature and U b0 show the unusual behavior of increasing linearly with an increase in temperature from 80 to 360 K for both Schottky contacts. The tunneling saturation (J TU ð0Þ) and tunneling parameters (E 0 ) were calculated for both Schottky contacts. We observed a weak temperature dependence of the saturation current and a fairly small dependence on the temperature of the tunneling parameters in this temperature range. The results indicate that the dominant mechanism of the charge transport across the Pt/p-InGaN and Pt/n-InGaN Schottky contacts are electron tunneling to deep levels in the vicinity of mixed/screw dislocations in the temperature range of 80-360 K

"Fairy Chimney'-Shaped Tandem Metamaterials as Double Resonance SERS Substrates

A highly tunable design for obtaining double resonance substrates to be used in surface-enhanced Raman spectroscopy is proposed. Tandem truncated nanocones composed of Au-SiO2-Au layers are designed, simulated and fabricated to obtain resonances at laser excitation and Stokes frequencies. Surface-enhanced Raman scattering experiments are conducted to compare the enhancements obtained from double resonance substrates to those obtained from single resonance gold truncated nanocones. The best enhancement factor obtained using the new design is 3.86 x 107. The resultant tandem structures are named after Fairy Chimneys rock formation in Cappadocia, Turkey

High Power K-band GaN on SiC CPW Monolithic Power Amplifier

This paper presents a high power amplifier at K-band (20.2 - 21.2 GHz). The AlGaN/GaN CPW MMIC amplifier is realized with 0.25 mu m HEMT process on 2-inch semi-insulating SiC substrate. The amplifier has a small signal gain over 20 dB for Vds=15V and measured output power of over 31 dBm at 20.2 Ghz. PAE of the amplifier is around 22% for desired frequency band. Initial radiation hardness tests indicate a suitable stability of the technology in space

Development of AZO TCOs with ALD for HEMT and HJSC solar cell applications

Transparent Conductive Oxide (TCO) films are widely used in optoelectronic devices, such as solar cells, LEDs, and Lasers. Utilization of these contacts directly affects the device efficiencies. These films can be produced with solid, liquid and vapor phase deposition techniques. Generally, metal oxides such as CdO, In2O3, SnO2, Ga2O3 and ZnO can be used in these structures as intrinsic or extrinsic semiconductors. Purpose of this study is to reproduce widely studied Aluminium doped Zinc Oxide (AZO) using a vapor phase technique, Atomic Layer Deposition (ALD) and optimize the doping concentration, electrical and optical properties, thickness for (n+) a-Si:H surface of silicon heterojunction solar cells (HJSCs) and high electron mobility transistor (HEMT) applications. The results show that as-deposited films have 80-90% transmittance in the visible spectra, low resistance (1.57x10-3 ohm.cm) and good mobility (10.69 cm2/V.s)

Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors

Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption–dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively

Development of AZO TCOs with ALD for HEMT and HJSC Solar Cell Applications

Transparent Conductive Oxide (TCO) films are widely used in optoelectronic devices, such as solar cells, LEDs, and Lasers. Utilization of these contacts directly affects the device efficiencies. Purpose of this study is to produce and optimize properties of Aluminum doped Zinc Oxide (AZO) using a vapor phase technique, Atomic Layer Deposition (ALD) for (n+) a-Si:H surface of silicon Heterojunction Solar Cells (HJSCs) and High Electron Mobility Transistor (HEMT) applications. This study is focused on the effect of the deposition temperature and aluminum atomic concentration on structural, electrical and optical properties of ALD grown AZO ohmic contact films. The results show that as-deposited films have 80-90% transmittance in the visible spectra, low resistance (2.04x10-3 ohm.cm) and mobility value of 5.25 cm2/V.s