We have fabricated two-tiered heterostructures consisting of phosphorus δ-doped Si quantum dots (Si-QDs) and undoped Si-QDs and studied their electron field emission properties. Electron emission was observed from the P-doped Si-QDs stack formed on the undoped Si-QDs stack by applying a forward bias of ∼6 V, which was lower than that for pure Si-QDs stack. This result is attributed to electric field concentration on the upper P-doped Si-QD layers beneath the layers of the undoped Si-QDs stack due to the introduction of phosphorus atom into the Si-QDs, which was positively charged due to the ionized P donor. The results lead to the development of planar-type electron emission devices with a low-voltage operation.

The Seebeck coefficient of Si wire co-doped with P and Ga atoms is investigated for applying thermoelectric devices. The observed Seebeck coefficient is closed to the theoretical values of electronic part of Seebeck coefficient due to the electronic transport. From the estimation of phonon scattering processes, it is found that the phonon-drag contribution to the Seebeck coefficient in co-doped Si wire is mainly governed by the phonon-boundary scattering.

Although the Tunnel Field-Effect Transistor (TFET) is a promising device for ultra-low power CMOS technology due to the ability to reduce power supply voltage and very small off-current, there have been few reports on the control of VT for TFETs. Unfortunately, the TFET needs a different technique to adjust VT than the MOSFET by channel doping because most of TFETs are fabricated on SOI substrates. In this paper, we propose a technique to control VT of the TFET by putting an additional VT-control doping region (VDR) between source and channel. We examine how much VT is changed by doping concentration of VDR. The change of doping concentration modulates VT because it changes the semiconductor work function difference, ψs,channel-ψs,source, at off-state. Also, the effect of the size of VDR is investigated. The region can be confined to the silicon surface because most of tunneling occurs at the surface. At the same time, we study the optimum width of this region while considering the mobility degradation by doping. Finally, the effect of the SOI thickness on the VDR adjusted VT of TFET is also investigated.

To achieve conductive and wear-durable carbon thin films by metal doping, we deposited Au-, Pt-, and Pd-doped carbon thin films by RF sputtering, and evaluated the dopant concentrations, resistivity, and scratch hardness. Among the doped films, the Pt-doped film with low Pt concentration was most suitable from a practical perspective.

To realize highly conductive and wear-durable thin films, we deposited metal doped carbon films onto silicon substrates by RF sputtering method. The dopant metals were various precious metals and transition metals. The electrical conductivity and wear durability of the deposited films were evaluated. We have found that Ir doping especially increased the electrical conductivity for the given amount of dopant metal. The wear durability of Ir-doped carbon films did not deteriorate even below a 7 at.% Ir concentration, and the conductivity of 7 at.% Ir-doped carbon was twenty times that of a non-doped carbon thin film.

One of 3-D devices to achieve high density arrays was adopted in this study, where source and drain junctions are formed along the silicon fin. The screening by adjacent high fins for large sensing margin makes it hard to ion-implant with high angle so that vertical ion implantation is inevitable. In this study, the dependency of current characteristics on doping profiles is investigated by 3-D numerical analysis. The position of concentration peak and the doping gradient are varied to look into the effects on driving currents. Through these analyses, the optimum condition of ion implantation for 3-D devices is estimated.

In this paper, we report a new collector-up npn heterojunction bipolar transistor (C-up HBT) which employs a p-type doping buried layer inserted between extrinsic emitter and subemitter for current confinement. A theoretical study is performed to verify the functionality of the p-type doping buried layer using a two-dimensional device simulator. The structural parameters of the device and bias conditions on the buried layer are investigated to understand the limitations and the potential of devices. It is found that the emitter structure should be optimized to achieve the high efficiency of current confinement and the design of overlap between base-collector junction and buried layer is effective to suppress the carrier-blocking effect. Moreover, proposed C-up HBT demonstrates the similar current-gain cutoff frequency (fT) characteristics compared with conventional C-up HBT fabricated by ion implantations. The impact of fT caused by the external base-emitter capacitance (CBE,ext) can be relieved by further structural optimization of the emitter layer and lateral scaling of the extrinsic region. To clarify the feasibility of the proposed C-up HBTs, we also specify the fabrication process for the devices with epitaxial regrowth techniques.

CMOS poly-Si thin-film transistors (TFTs) were fabricated through crystallization and GILD processes by a novel selected area laser assisted (SALA) system. The system enables a local area irradiation of small beams of a pulsed solid-state laser of frequency tripled Nd:YAG. The novel TFT process eliminated 3 doping mask steps of the conventional process. On-off current ratios for both types of poly-Si TFTs were improved by SALA. The field effect mobility of n- and p-channel TFTs is 84 cm2/Vs and 75 cm2/Vs, respectively.

A thin high-doping layer was inserted in the uniform doped collector to extend the operational current before current gain and cut-off frequency roll-off. Two times higher collector current before onset of Kirk effect was obtained and the resulted John figure of merit was improved from 846 to 1008 V-GHz.

Field emission display (FED) is evolving as a promising technique of flat panel displays in the future. In this paper, various carbon based nanostructures are acted as cathode materials for field emission devices. Dendrite-like diamond-like carbon emitters, carbon nanotubes, carbon nanotips are synthesized by microwave plasma chemical vapor deposition. Many factors affect the performance of field emitters, such as the shape, work function and aspect ratio of emission materials. Modified process of carbon based nano-materials for enhancing field emission efficiency are included intrinsic and extrinsic process. These reformations contain the p-type and n-type doping, carburization and new ultra well-aligned carbon nano-materials. It is found that carbon nano-materials grown on micropatterned diode show higher efficiency of FED. In addition, to achieve a low- turn-on field, the novel scheme involving a new fabrication process of gated structure metal-insulator-semiconductor (MIS) diode by IC technology is also presented.

In this work, we review our recent efforts to make effective use of atomistic calculations for the advancement of VLSI process simulation. We focus on three example applications: the behavior of implanted fluorine, arsenic diffusion and activation, and the impact of charge interactions on doping fluctuations.

Monte Carlo simulation of the low field electron mobility of strained Si and SiGe active layers on Si and SiGe substrates is considered. The Ge mole fractions of both the active layer and the substrate are varied in a wide range. The linear deformation potential theory is used to calculate the shifts of the conduction band minima due to uniaxial strain along [001]. The energy shifts and the effective masses are assumed to be functions of the Ge mole fraction. It is shown that in spite of the fact that the L-valleys remain degenerate under strain conditions considered here, they play an important role at very high Ge compositions especially when SiGe as substrate is used. We found that in this case the repopulation effects of the X-valleys affect electron mobility much stronger than the alloy scattering. We also generalize the ionized impurity scattering rate to include strain effects for doped materials and show that some of the important parameters such as effective density of states, inverse screening length, and the screening function are split due to strain and must be properly modified. Finally, we perform several simulations for undoped and doped materials using Si and SiGe substrates.

Laser induced boron doping of silicon is studied as a function of the laser pulse number and energy density, in a special configuration where the precursor gas (BCl3) is injected and chemisorbed on the Si surface prior to each laser pulse. In-situ optical diagnostics, based on the transient reflectivity at 675 nm, allow to control the evolution of the dopant concentration and of the doped layer thickness during the laser doping process. Samples are characterized by the four-point probe method, atomic force microscopy (AFM) and secondary ion mass spectrometry (SIMS). As the laser pulse number is scanned from 10 to 200 at a constant laser pulse energy, the junction depth increases from 21 to 74 nm while its sheet resistance decreases from 220 to 17 Ω/. Moreover, boron concentrations well above the solubility limit (up to 31021 cm-3 for 200 pulses) and very abrupt box-like dopant profiles are obtained. So, laser doping, in this dopant gas injection configuration, seems to be a very attractive technique to meet the International Technology Roadmap for Semiconductors (ITRS) requirements for ultra-shallow junctions.

785 nm (AlGaAs) laser diode (LD) with a window-mirror structure is demonstrated to be a potential candidate as a highly reliable light source of CD-R. The intermixing of a multi-quantum well structure by silicon implantation is used to form the window-mirror structure. Carbon is adopted as an acceptor because of its low thermal diffusion constant in crystals. As a result, the window-mirror-structure 785 nm AlGaAs LDs with ordinary far field patterns suitable for the actual CD-R drives have shown stable single lateral mode operation up to 250 mW. A mirror degradation level is significantly increased by the window-mirror structure. The pulsed operation current at 160 mW, 70 of the carbon doped LD is reduced by about 15% from that of zinc doped one. Highly reliable 160 mW pulsed operation is also realized at 70. This LD believed to be suited for the next generation high-speed (16-24x) CD-R drives necessitating 160 mW class LD.

We present novel semiconductor technologies of ZnO epitaxial films with using laser molecular-beam epitaxy method. Exciting optical properties such as room temperature lasing in ZnO nanocrystalline films and quantum size effects in ZnO/MgxZn1-xO superlattices were observed. By developing crystalline quality with using lattice-matched substrates, we could control resistivity of the doped ZnO films from 10-3 Ωcm to 104 Ωcm. These results would provide us an opportunity to construct a monolithic array consisted of light emitting devices and field effect transistors towards a possible flat panel display.

We demonstrate unique dye-doping method to realize organic light emitting diodes (OLED) with high efficiency, high brightness and pure red emission. In this study, we used 5,10,15,20 tetraphenyl -21H,23H-porphine (TPP) as emitting dopant into 8-hydroxyquinoline aluminum (Alq3) emissive layer. To improve turn-on voltage and emission characteristics, a sufficient amount of 4-(dicyano methylene) -2-methyl -6-(p-dimethyl aminostyryl) -4H-pyran (DCM) was added to the TPP doped Alq3 emissive layer. The mechanisms and the emission characteristics of the co-doped EL device are discussed using energy band diagram of the materials used in the device.

We studied Si and Mg doping characteristics in cubic GaN and fabricated a light emitting diode of cubic GaN on a GaAs substrate by metalorganic vapor-phase epitaxy. The diode structure consisted of undoped and Mg-doped GaN stacking layers deposited on Si-doped GaN and AlGaN layers. The electron-beam-induced-current signal and current injection characteristics of this diode structure were measured. There was a peak at the interface between the Mg-doped and undoped GaN in the electron-beam-induced-current signal. This shows successful growth of the p-n junction. Light emitting operation was achieved by currents injected through the conducting GaAs substrate of this diode at room temperature. We observed electroluminescence below the bandgap energy of cubic GaN with a peak at 2.6 eV.

Carbon-doped base InP/InGaAs heterojunction bipolar transistor (HBT) technology for millimeter-wave application is presented. Ultra-high carbon doping of InGaAs layers lattice-matched to InP with hole concentrations in excess of 1 1020 /cm3 has been achieved using a chemical beam epitaxy (CBE). Heavily carbon-doped base InP/InGaAs HBT epi structures were grown and small area, self-aligned HBTs with 1.5 µm emitter finger width were fabricated using triple mesa etching and polyimide planarization techniques. The fabricated small area transistors showed a common-emitter current gain cut-off frequency (fT) as high as 200 GHz. Preliminary device reliability test results showed the potential of the heavily carbon-doped base InP/InGaAs HBT for high performance microwave and millimeter-wave applications. Applications of the InP/InGaAs single heterojunction bipolar transistor (SHBT) and double heterojunction bipolar transistor (DHBT) to a direct-coupled feedback amplifier and a power transistor, respectively, are presented.

We propose a new inverse modeling method to extract 2D channel dopant profile in an MOSFET. The profile is extracted from threshold voltage (Vth) of MOSFETs with a series of gate lengths. The uniqueness of the extracted channel and drain profile is confirmed through test simulations. The extracted profile of actual 0.1 µm nMOSFETs explains reverse short channel effects (RSCE) of threshold voltage dependent on gate length including substrate bias dependence.

SiGe HBTs with doping level inversion, that is, a higher dopant concentration in the base than in the emitter, are realized based on the double-polysilicon self-aligned transistor scheme by means of selective epitaxy performed in a production CVD reactor. The effects of the Ge profile in the base on the transistor performance are explored. The fabricated HBT with a 12-27% graded Ge profile demonstrates a maximum cutoff frequency of 88 GHz, a maximum oscillation frequency of 65 GHz, and an ECL gate delay time of 13.8 ps.