4 research outputs found
Recommended from our members
Investigation of metal-insulator-metal (MIM) and nanolaminate barrier MIIM tunnel devices fabricated via atomic layer deposition
Metal-insulator-metal (MIM) tunnel devices have been proposed for high speed applications such as hot electron transistors, IR detectors, optical rectennas for IR energy harvesting, and backplanes for LCDs. The majority of these applications require highly asymmetric and non-linear current versus voltage (I-V) behavior at low applied voltages and ultra-high frequencies. The objective of this work is to develop MIM tunnel devices with improved electrical properties including I-V asymmetry and non-linearity. The standard approach to achieving asymmetric operation in MIM devices is through the use of electrodes with different metal work functions. This approach is investigated using a variety of thin film dielectrics deposited by atomic layer deposition (ALD). To assess suitability for high speed operation, the physical mechanisms of electron transport in each dielectric are investigated. Next, as an alternative approach to achieving asymmetric and non-linear operation, pairs of dielectrics with different band-gaps and band-offsets are combined to form asymmetric tunnel barrier metal-insulator-insulator-metal (MIIM) diodes. MIIM diodes are fabricated using ALD to form nanolaminate pairs of Al₂O₃, HfO₂, ZrO₂, and Ta₂O₅ between asymmetric electrodes. It is found that the performance of the MIIM diodes is sensitive to the choice, relative thickness, and arrangement of the individual dielectric layers. It is shown that asymmetric dual-dielectric tunnel barriers can overwhelm the influence of asymmetric electrodes and it is demonstrated that MIIM structures can be designed to provide improved asymmetry at low electric fields. Low field asymmetry improvements are shown to be due to a step tunneling phenomenon. Finally, the formation and influence of interfaces, as a means for providing insight into engineering of nanolaminate barrier tunnel devices is examined by comparing different atomically smooth bottom electrodes
Recommended from our members
Enhancing metal-insulator-insulator-metal tunnel diodes via defect enhanced direct tunneling
Metal-insulator-insulator-metal tunnel diodes with dissimilar work function electrodes and nanolaminate Al₂O₃-Ta₂O₅ bilayer tunnel barriers deposited by atomic layer deposition are investigated. This combination of high and low electron affinity insulators, each with different dominant conduction mechanisms (tunneling and Frenkel-Poole emission), results in improved low voltage asymmetry and non-linearity of current versus voltage behavior. These improvements are due to defect enhanced direct tunneling in which electrons transport across the Ta₂O₅ via defect based conduction before tunneling directly through the Al₂O₃, effectively narrowing the tunnel barrier. Conduction through the device is dominated by tunneling, and operation is relatively insensitive to temperature
Recommended from our members
Conduction processes in metal–insulator–metal diodes with Ta₂O₅ and Nb₂O₅ insulators deposited by atomic layer deposition
Metal–insulator–metal diodes with Nb₂O₅ and Ta₂O₅ insulators deposited via atomic layer deposition are investigated. For both Nb₂O₅ and Ta₂O₅, the dominant conduction process is established as Schottky emission at small biases and Frenkel–Poole emission at large biases. Fowler–Nordheim tunneling is not found to play a role in determining current versus voltage asymmetry. The dynamic dielectric constants are extracted from conduction plots and found to be in agreement with measured optical dielectric constants. Trap energy levels at ϕT ≈ 0.62 and 0.53eV below the conduction band minimum are estimated for Nb₂O₅ and Ta₂O₅, respectively.This is the publisher’s final pdf. The article is copyrighted by the American Vacuum Society and published by the American Institute of Physics Publishing
Recommended from our members
Investigation of the impact of insulator material on the performance of dissimilar electrode metal-insulator-metal diodes
The performance of thin film metal-insulator-metal (MIM) diodes is investigated for a variety of large and small electron affinity insulators using ultrasmooth amorphous metal as the bottom electrode. Nb2O5, Ta2 O5, ZrO2, HfO2, Al2 O3, and SiO2 amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss spectroscopy (REELS) is utilized to measure the band-gap energy (EG) and energy position of intrinsic sub-gap defect states for each insulator. EG of as-deposited ALD insulators are found to be Nb2O5¼3.8 eV, Ta2O5¼4.4 eV, ZrO2¼5.4 eV, HfO2¼5.6 eV, Al2O3¼6.4 eV, and SiO2¼8.8 eV with uncertainty of 60.2 eV. Current vs. voltage asymmetry, non-linearity, turn-on voltage, and dominant conduction mechanisms are compared. Al2O3 and SiO2 are found to operate based on Fowler-Nordheim tunneling. Al2O3 shows the highest asymmetry. ZrO2, Nb2O5, and Ta2O5 based diodes are found to be dominated by Frenkel-Poole emission at large biases and exhibit lower asymmetry. The electrically estimated trap energy levels for defects that dominate Frenkel-Poole conduction are found to be consistent with the energy levels of surface oxygen vacancy defects observed in REELS measurements. For HfO2, conduction is found to be a mix of trap assisted tunneling and Frenkel-Poole emission. Insulator selection criteria in regards to MIM diodes applications are discussed.This is the publisher’s final pdf. The published article is copyrighted by the American Institute of Physics Publishing and can be found at: http://scitation.aip.org/content/aip/journal/jap.Keywords: Conduction, Gate dielectric stacks, Transisto