Abstract-Here we explore the performance limit of monolayer germanane (GeH) field-effect transistors (FETs). We first plotted an electronic band structure of GeH using density functional theory (DFT) and then tight-binding parameters were extracted. Device characteristics of GeH FETs are investigated using rigorous self-consistent atomistic quantum transport simulations within tight-binding approximations. Our simulation results indicate that GeH FETs can exhibit exceptional on-state device characteristics such as high I on (>2 mA/µm) and large g m (~7 mS/µm) with V DD = 0.5 V due to the very light effective mass of GeH (0.07m 0 ), while maintaining excellent switching characteristics (SS ~64 mV/dec). We have also performed a scaling study by varying the channel length, and it turned out that GeH FET can be scaled down to ~14 nm channel without facing significant short channel effects but it may suffer from large leakage current at the channel length shorter than 10 nm. channel material have rarely explored although it has great potential for future electronic devices toward various applications. The performance of GeH FET was estimated previously by semi-classical model [10], but such a simple approach can be significantly limited in predicting the detailed characteristics of germanane device, where quantum-mechanical treatment will be critical to discuss tunneling and scaling. Therefore, in this work, we investigate the performance limit of GeH FET using rigorous self-consistent atomistic quantum transport simulations. Our simulation results exhibit superior on-state characteristics of GeH FET with excellent switching behaviors. However, due to the very light effective mass, the scaling of GeH FET can be significantly limited as it suffers from large leakage current. We have also benchmarked GeH FET against MoS 2 counterpart, which indicates that GeH FET has clear benefits for high-performance applications compared to a similar device based on MoS 2 .
II. SIMULATION METHODSDensity functional theory (DFT) calculation [11] was utilized to obtain the band structure of GeH. Generalized gradient approximations (GGA) exchange correlation function using PBE parameterization was employed for the DFT calculation. For a geometry optimization, conjugate-gradients (CG) was used with maximum force tolerance of 10 -3 eV/Å and energy tolerance of 10 -4 eV. The unit cell of germanane contains two germanium atoms and two hydrogen atoms as shown in the inset of Fig. 1 (a). The Brillouin zone sampling was done using Monkhorst-Pack approach with a 50×50×1 mesh. The calculated band structure is shown in Fig. 1(a This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at http://dx
We have developed a piezoelectric microvalve with a silicon seat for the propulsion system of a micro-satellite. The silicon seat is fabricated with narrow sealing rings to reduce internal leaks. The fatigue performance of the silicon seat is characterized. The lifetime of the silicon seat without coating is approximately 25 000 times, which cannot meet the requirement for astronautic applications. To improve its fatigue performance, the silicon seat is deposited with Cu and parylene, respectively. The two seats both meet the sealing requirement after 10 5 cycle operation. Several rings of the seats deposited with Cu fractured after the fatigue tests, whereas none of the rings of the seats deposited with parylene fractured due to the obvious reduction of the impact stress.
Using self-consistent atomistic quantum transport simulations, the device characteristics of n-type and p-type germanane (GeH) field-effect transistors (FETs) are evaluated. While both devices exhibit near-identical off-state characteristics, n-type GeH FET shows ~40% larger on current than the p-type counterpart, resulting in faster switching speed and lower power-delay product. Our benchmark of GeH FETs against similar devices based on 2D materials reveals that GeH outperforms MoS 2 and black phosphorus in terms of energy-delay product (EDP). In addition, the performance of GeH-based CMOS circuit is analyzed using an inverter chain. By engineering power supply voltage and threshold voltage simultaneously, we find the optimal operating condition of GeH FETs, minimizing EDP in the CMOS circuit. Our comprehensive study including material parameterization, device simulation, and circuit analyses demonstrates significant potential of GeH FETs for 2D-material CMOS circuit applications.
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