A. M. Khairul

Single and dual strained channel analysis of vertical strained — SiGe impact ionization MOSFET (VESIMOS)

Single Channel (SC) and Dual Channel (DC) Vertical Strained-SiGe Impact Ionization MOSFET (VESIMOS) has been successfully simulated and analyzed in this paper. Found out that SC VESIMOS operate in conventional MOSFET mode at V_DS = 1.75V, with 10% to 30% Ge mole fraction. However for Ge=50%, its operated in Impact Ionization (II) mode with fast switching speed of subthreshold value, S=9.8 mV/dec. A better performance in threshold voltage, V_TH, S value and I_ON/I_OFF ratio were found in DC VESIMOS as compared to SC VESIMOS. The V_TH=0.6V, S=10.98 mV/dec and I_ON/I_OFF = 1×10¹³ were measured in DC VESIMOS with Ge=30% that clarify the advantage of DC utilization on VESIMOS device. These improvements were mainly due to the enhancement of electron mobility from 600 m²/V-s (first channel) to 1400 m²/V-s (second channel). The electron mobility was increased due to the splitting of conduction band valley into six fold where the electron mass are reduced in out of plane direction and thus enhanced the mobility of electron.

Impact of strain and DP position on the performance of Vertical Strained-SiGe Impact Ionization MOSFET incorporating dielectric pocket (VESIMOS-DP)

The Vertical Strained Silicon Germanium (SiGe) Impact Ionization MOSFET with Dielectric Pocket (VESIMOS-DP) has been successfully developed and analyzed in this paper. The strain is induced in the structure by varying the mole fraction of Silicon Germanium layer as well as the channel thickness. Increase in mole fraction at the interface of channel region results in increase in strain in the channel. In order to maintain strain in the channel region, a relaxed Si1-xGex layer is required. S value for DP place at source side is higher (S=24.4 mV/decade) as compared at the drain side (S=18.9 mV/decade) intrinsic region. The impact ionization rate depends on the electric field at drain side intrinsic zone. The vicinity of DP near the drain region reduces charge sharing effects associated with the source and thus improves impact ionization rate. Due to the DP layer, improve stability of threshold voltage, VTH and subthreshold slope, S was found for VESIMOS-DP device of various size ranging from 20nm to 80nm which justified the vicinity of DP on improving the performance of the device.

Enhancing efficiency of organic solar cells by interfacial materials modification

This paper directed towards enhancing power conversion efficiency of organic photovoltaic by exploring emerging non-conjugated polymer material as an interfacial layers. The effect of non-conjugated polar polymers such as polymethyl methacrylate (PMMA), poly(4-vinylpyrirolidone) (PVPy) and poly(4-vinylalcohol) (PVA) as an interfacial layer (IFL) at the cathode side in improving the efficiency of poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) OPV cell. The best power conversion efficiency (pCE) for OPVs with PVPy film currently is about 3.51% compared to the OPVs without the PVPy film which is about 2.88%. Efficiency enhancement of OPVs with PVA and PMMA film, PCE=3.27% and 3.39% respectively shows that the addition of those interfacial layers between the cathode interfaces had improve charge carrier mobility relative to the devices lacking those materials. This is reflected on the enhancement of open circuit voltage, short circuit current and fill factor value of these OPV device. The introduction of interfacial layer materials to OPV device also had reduce the work function of Al and enhanced short circuit current of OPV device. This eventually improves the reliability and efficiency rate of OPV for future building integrated photovoltaic application.

Does magnetic nano-materials in plane impedance vital for RF loss assessment?

RF (radiofrequency) system core size reduction is essential to operate it efficiently in RF power and sub-system. In this drive system power loss minimization at controlled volume is the key feature. Magnetic nano-materials higher permeability enhance functionality, energy efficiency is related to device power density and system miniaturization. The major RF heating loss is associated to in plane impedance that is varied due to applied field and frequency band. Presenting impedance plane simulation software; resistance as well as inductive reactance at particular frequency band have been evaluated thus RF power loss is realized. Nano-crystalline core lowest resistance linked to highest conductivity appears to be potential for device shrinking, RF power and sub-system loss minimization.

Enhanced reliability of vertical strained impact ionization MOSFET incorporating dielectric pocket for ultra-sensitive biosensor applications

Fast switching with an enhanced reliability device structure of Vertical Strained Impact Ionization MOSFET incorporating Dielectric Pocket (VESIMOS-DP) has been successfully design, simulated and analyzed in this paper. Ultra-low power with low subthreshold swing (S) and high breakdown voltage are imperative for ultra-sensitive biosensors. Impact ionization MOSFET (IMOS) is predicted to be capable of S as low as 20 mV/dec, which is much lower than Conventional MOSFET (CMOS). There are significant drop in subthreshold slope (S) while threshold voltage is increase as the body doping concentration increases. S value for DP place at source side is higher (S 24.4 mV/decade) as compared at the drain side (S 18.9 mV/decade) intrinsic region. The vicinity of DP near the drain region reduces charge sharing effects associated with the source and thus improves impact ionization rate. The introduction of a Dielectric Pocket (DP) is believed to be able to minimize the PBT effect while improving the reliability of the device by attaining higher breakdown voltage. Consequently, with the reduced of alloy scattering, the electron mobility has been improved by 22%. In many aspects, it is revealed that the incorporation of DP enhanced the reliability of VESIMOS for future development of nanoelectronic devices.

Characterization of vertical strained SiGe impact ionization MOSFET for ultra-sensitive biosensor application

This paper venture into prospective ideas of finding viable solution of nanoelectronics device design by an assessment of incorporating vertical impact-ionization MOSFET (IMOS) with strained SiGe technology into a formation of an emerging device structure with elevated performance and reliable outcomes for future bio-based sensor application. Impact Ionization FET biosensors can be extremely promising for applications where ultra-high sensitivity and fast response is desirable. An ultra-low power with low Subthreshold Swing and high breakdown voltage are imperative for ultra-sensitive biosensor. Impact ionization MOSFET (IMOS) is expected to have a subthreshold swing (S) down to 20 mV/dec which is much lower compared to Conventional MOSFET (CMOS). This will eventually enhanced the switching behavior of the transistor and enhancing its electrical performance and response time particularly when scaled down into nanometre regime. However, vertical IMOS experience parasitic bipolar transistors (PBT) effect and low breakdown voltage. Parasitic Bipolar Transistor effect is a phenomenon where the MOSFET act as a minority carrier device like BJT instead of majority carrier device. This is not favorable for any power device or sensor. Dielectric Pocket (DP) is believed to be able to minimize the PBT effect while improving the performance of the device. Eventually, this device will prolong the increase density of transistor in a chip for future application of biosensor nanoelectronics.

Body doping analysis of vertical strained-SiGe Impact Ionization MOSFET incorporating dielectric pocket (VESIMOS-DP)

The Vertical Strained Silicon Germanium (SiGe) Impact Ionization MOSFET with Dielectric Pocket (VESIMOS-DP) has been successfully developed and analyzed in this paper. There are significant drop in subthreshold slope (S) while threshold voltage is increase as the body doping concentration increases. It is notable that for body doping concentration above 1020, the S values keep increasing which is not recommended as the switching speed getting higher distracting performance of the device. An improved stability of threshold voltage, VTH was found for VESIMOS-DP device of various DP size ranging from 20nm to 80nm. The stability is due to the reducing charge sharing effects between source and drain region. In addition, the output characteristic was also highlighted a very good drain current at different gate voltage with the increasing of drain voltage for VESIMOS-DP with high body doping concentration. VESIMOS-DP with low body doping concentration suffers PBT effect that prevents the device from being able to switch off. Hence, high body doping concentrations are imperative for obtaining better device characteristics and ensure the device works in II mode.

Mobility enhancement on Vertical Strained-SiGe Impact Ionization MOSFET incorporating Dielectric Pocket (VESIMOS-DP)

The Vertical Strained Silicon Germanium (SiGe) Impact Ionization MOSFET with Dielectric Pocket (VESIMOS-DP) has been successfully developed and analyzed in this paper. The electron mobility in the VESIMOS-DP (~1440m2/V-s), was found to be increased by 4% in comparison to VESIMOS (~1386 m2/V-s) device. The mobilities in strained layer is depends on the transport direction, either parallel to the original SiGe growth interface or in the perpendicular direction. Carrier mobilities in strained SiGe layer is also based on the local distortion due to the strain effects which contribute to the alloy scattering on the carriers. With the vicinity of DP, the carrier scattering effect has reduced which merits the introduction of DP on the device. Due to the DP layer, improve stability of threshold voltage, VTH and subthreshold slope, S was found for VESIMOS-DP device of various size ranging from 20nm to 80nm justified the vicinity of the DP on improving the performance of the device.

Energy Spectrum and Carrier Statistics Numerical Analysis for Nanostructure Device Application

Numerical analysis of energy spectrum and carrier statistics for nanostructure device application is presented. The low-dimensional energy spectrum was successfully derived for the respective quasi 3D, 2D and ID system that invoked the effect of quantum confinement (QCE) comparable to the De Broglie wavelength (λD ≅ 10nm). For non-degenerately (ND) doped samples the Fermi-Dirac (FD) integral is well approximated by Boltzmann statistics. However, in degenerate doped quasi 3D, 2D and ID device, the FD integral is found to be approximated by order one-half, zero and minus one-half respectively. The Fermi energy is revealed to be a weak (logarithmic) function of carrier concentration, but varies linearly with temperature in the ND regime. However, for strongly degenerate statistics, the Fermi energy is independent of temperature and is a strong function of carrier concentration.