Tunnel FET (TFET) has potential applications in the next generation ultra-low power transistor to substitute the conventional FETs. It can offer very steep inverse subthreshold swing slope to maintain a low leakage current, thus it can be very essential for limiting power consumption in MOSFETs. The carriers in TFET transport from source to channel by the band-to-band tunneling (BTBT) mechanisms. To realize high saturation currents of TFET, it critically depends on the transmission probability, T WKB . In indirect semiconductor, such as Si and Ge, the BTBT model is very crucial for designing and predicting the device performance. In this paper, we employed the nonlocal BTBT model applied to three-dimensional Ge-Si heterojunction TFET with gate length 10 nm compare with Si TFET by including quantum effects simulation. The results show that the Ge-Si TFET outperforms Si TFET because of the lower bandgap and larger tunneling windows. BTBT generation rates of Ge-Si TFET are higher than Si TFET in the on-state condition. The highest BTBT generation rates are located in the source and channel junction and its peaks close to the gate dielectric. Power dissipation is a primary concern for future nanoelectronics devices and switching systems.1 Reducing supply voltage (V DD ), while keeping leakage current very low is very essential for limiting power consumption in MOSFETs.2 As V DD is reduced, the overdrive factor (V DD -V TH ) must be remained high to meet performance requirements. On the other hand, reducing threshold voltage (V TH ) can cause the off-state current (I OFF ) increase exponentially. Therefore, subthreshold swing (SS) must be reduced to maintain a low I OFF . However, conventional MOSFETs cannot provide SS lower than 60 mV/dec at room temperature because of fundamental thermal limits. Charge injection in the MOSFETs occurs by thermionic emission over a potential barrier, is bound by an exponential tail of Fermi statistics. 3,4 In the nanoscale transistor, the cylindrical nanowire is the promising candidate in the ultra-low power vertical devices due to high device density, its negligible trapping and leakage from buffer layer, wrap-gated structure and possibility of very short gate length (below 20 nm).5 Moreover, cylindrical shape tunnel field-effect transistor (TFET) can offer a very steep inverse subthreshold slope for maintain a low leakage current. The TFET is a gated p-i-n transistor with a gate voltage that causes large band bending at the source junction. Hence, the carriers can be transported from source to channel by the band-to-band tunneling (BTBT) mechanism. 6 The carrier injection on the BTBT of electrons from a degenerate p+ source into the channel conduction band causes high-energy carrier are filtered out by the semiconductor bandgap. Thus, steeper subthreshold slopes can be achieved.
3Recent studies have reported many complex fabrication issues of TFETs because of asymmetric doping concentration in source and drain of planar horizontal TFET. For the mature material process like germaniu...
A silicon junctionless (JL) trench gate-all-around (GAA) nanowire field-effect transistor with an atomically thin channel thickness of 0.65 nm and a very thin oxide with a thickness of 12.3 nm are demonstrated experimentally. Experimental results indicate that this device with a channel thickness of 0.65 nm achieves a sub-threshold slope (SS) of 43 mV/decade, which is the best yet achieved by any reported JLFET. Owing to the atomically thin channel, this device has an extremely high ION/IOFF current ratio of >108. Furthermore, the atomically thin channel GAA JLFET exhibits a low threshold voltage (VTH) variation and negligible drain-induced barrier lowering (DIBL < 0.4 mV/V). The reported device with the thinnest channel has a very high band-to-band tunneling generation rate of 1.2 × 1024/cm2 s when the channel is scaled down to <1 nm, as confirmed by using the 3D quantum transport simulation tool. This quantum tunneling provides a means of achieving an SS value much lower than its fundamental physical limit.
The characteristic performance of n-type and p-type inversion (IM) mode, accumulation (AC) mode and junctionless (JL) mode, bulk Germanium FinFET device with 3-nm gate length (L G ) are demonstrated by using 3-D quantum transport device simulation. The simulated bulk Ge FinFET device exhibits favorable short channel characteristics, including drain-induced barrier lowering (DIBL<10mV/V), sub threshold slope (SS~64mV/dec.). Electron density distributions in ON-state and OFFstate also show that the simulated devices have large I ON /I OFF ratios. Homogenous source/drain doping is maintained and only the channel doping is varied among different operating modes. Also, a constant threshold voltage |V TH |~0.31V is maintained. Moreover, the calculated quantum capacitance (C Q ) values of the Ge nanowire emphasizes the importance of quantum confinement effects (QCE) on the performance of the ultra-scaled devices.
Micro/nanopatterns with micro deposition techniques have been used in various applications such as flexible electronic devices, biosensing, and biological tissue engineering. For depositing a small size of droplets that can be controlled, structured and patterned precisely is a very important process for microfabrication. In this study, we developed a low cost and simple system for fabricating micro/nanostructure by a selective micro deposition process using a syringe pump. This method is an additive fabrication method where selective droplet materials are released through a needle of the syringe pump. By translating the rotating stepper motor into a linear movement of the lead screw, it will press the plunger of the syringe and give a force to the fluid inside the syringe, hence a droplet can be injected out. The syringe pump system consists of a syringe, the mechanical unit, and the controller unit. A stepper motor, the lead screw, and the mechanical components are used for the mechanical unit. Arduino Uno microcontroller is used as the controller unit and can be programmed by the computer through GUI (Graphical User Interface). The input parameters, such as the push or pull of flow direction, flow rate, the droplet volume, and syringe size dimension can be inputted by the user as their desired value via keypad or the computer. The measurement results show that the syringe pump has characteristics: the maximum average error value of the measured volume is 2.5% and the maximum average error value of the measured flow rate is 14%. The benefits of a syringe pump for micro deposition can overcome photolithography weaknesses, which require an etching and stencil process in the manufacture of semiconductors. Combining two or more syringes into one system with different droplet materials can be used as a promising method for 3D microfabrication in the future.
We propose the use of Ge-cap quantum-well (QW) bulk FinFET for 5 nm CMOS integration, which is a Si channel wrapped with Ge around three sides of the fin channel. The simulation results show that the Ge-cap FinFET structure demonstrates better performance than pure Si, pure Ge, and Si-cap FinFET structures. By optimizing Si fin width and Ge-cap thickness, the on-state current of nFET and pFET can also be symmetric without changing the total fin width (F Wp = F Wn ). The electrons in Ge-cap nFinFET concentrate in the Si channel because of QWs formed in the lowest conduction band of the Ge and Si heterostructure, while the holes in Ge-cap pFinFET prefer to stay in Ge surfaces owing to QWs formed in the Ge valence band. The physics studies of this device have made the design rules relevant for the application of the CMOS inverter and static random access memory (SRAM) application technology.
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