Abstract: In this paper, we report on critical issues and possible solutions for realizing Ge MOSFETs on the Si platform. The main critical objectives in regard to Ge MOSFETs are (1) formation of high quality Ge channel layers on Si substrates (2) MIS gate stacks with much smaller EOT and interface defects (3) superior source/drain junction technology (4) combination of mobility booster technologies such as surface orientation and strain. We demonstrate that GeO2/Ge MOS interfaces can provide superior interface properties, leading to high hole and electron mobility. It is also shown that a gas phase doping technique is promising for forming superior n+/p junctions, which is critical for obtaining Ge nMOSFETs. Also, the importance of surface orientation engineering on the further mobility enhancement of Ge CMOS is addressed.
Abstract: We have investigated the Si-seeding rapid-melting process and demonstrated the formation of giant Ge stripes with (100), (110), and (111) orientations on Si (100), (110), and (111) substrates, respectively, covered with SiO2 films. We revealed that crystallization is triggered by Si-Ge mixing in the seeding regions in this process. Based on this mechanism, we have proposed a novel technique to realize orientation-controlled Ge layers on transparent insulating substrates by using Si artificial micro-seeds with (100) and (111)-orientations. This achieved epitaxial growth of single crystalline (100) and (111)-oriented Ge stripes on quartz substrates. The Ge layers showed a high hole mobility exceeding 1100 cm2/Vs owing to the high crystallinity.
Abstract: Hot phonon generation and its impact on the current conduction in a nanoscale Si-device are investigated using a Monte Carlo simulation technique. In the quasi-ballistic transport regime, electrons injected from the source lose their energies mainly by emitting optical phonons in the drain. Due to the slow group velocity of the optical phonons, the efficiency of the heat dissipation is so poor that a region with a nonequilibrium phonon distribution, i.e., a hot spot, is created. In this study, we have implemented the hot phonon effect in an ensemble Monte Carlo simulator for the electron transport, and carried out the steady state simulations. Although it is confirmed that the optical phonon temperature in the hot spot is larger than that of acoustic phonons by > 100 K, the electron current density is not significantly affected. The local heating would degrade the hot electron cooling efficiency and the parasitic resistance in the drain, but they have a minor impact on the quasi-ballistic electron transport from the source to the drain.
Abstract: The particular physical functions of quantum-sized silicon have been investigated, along with exploration of their potential device applications. A strong confinement effect fully modifies the original optical, electrical, and thermal properties of bulk silicon. A discussion regarding their control and applications is presented, which addresses blue phosphorescence, enhanced photoconduction, operation of a ballistic electron emitter in solutions, and digital drive of a thermo-acoustic sound emitter.
Abstract: An individual dopant atom may become the active unit of future electronic devices by mediating single-electron transport in nanoscale field-effect transistors. Single dopants can be accessed electrically even in a dopant-rich environment, offering the opportunity to develop applications based on arrays of dopants. Here, we focus on single-electron turnstile operation in arrays of dopant-induced quantum dots realized in highly-doped nanoscale transistors. We show that dopant-based single-electron turnstile can be achieved and tuned with a combination of two gates and we indicate guidelines for further optimization.
Abstract: Low temperature Kelvin Probe Force Microscopy (LT-KFM) can be used to monitor the electronic potential of individual dopants under an electric field. This capability is demonstrated for silicon-on-insulator field-effect-transistors (SOI-FETs) with a phosphorus-doped channel. We show results of the detection of individual dopants in Si by LT-KFM. Furthermore, we also observe single-electron charging in individual dopants located in the Si channel region.
Abstract: We have investigated C-V and photoluminescence (PL) characteristics of ultra-thin silicon-on-insulator (SOI) samples. Thickness dependence of a free exciton (FE) PL and an electron-hole droplet (EHD) PL has been investigated. We have found a remarkable enhancement of an EHD PL with decrease in the thickness of SOI samples.
Abstract: Ohmic contacts are crucial for both device applications and the study of fundamental physics. From the perspective of device scaling trends, nano-scale Ohmic contacts are indispensable for future LSI technologies such as metallic source and drain contacts. In this study, we investigate the I-V characteristics using a varying discrete level distribution based on our previously-proposed model. Our calculated results show that linear I-V properties can be obtained from uniform discrete level distributions.
Abstract: We study the sweep speed dependence of electron injection voltage in Si-Nano-Dots (Si-NDs) floating gate MOS Capacitor by using our collective tunneling model, which models the tunneling between two-dimensional electron gas (2DEG) and the Si-NDs. We clarify the sweep speed dependence of electron injection energy with a numerical calculation based on our collective tunneling model, that we developed to emulate the experiment in this system, and obtained a new insight into the origin of sweep speed dependence. We revealed that our model can reproduce the sweep speed dependence of electron tunneling. This insight is useful for designing future nano-electronic devices.