Junction Doping Research Articles

Low-Noise Avalanche Photodiode With Graded Junction in 0.15-<inline-formula> <tex-math notation="TeX">$\mu{\rm m}$ </tex-math></inline-formula> CMOS Technology

This letter presents the experimental characterization and noise modeling of a CMOS avalanche photodiode with pwell/n-iso active junction fabricated in a 0.15-μm standard CMOS process. The device exhibits a remarkably low excess noise factor F = 6 at a gain M = 50 in the blue spectral region, and F = 12 at M = 50 in the near-infrared. Gain and noise characteristics are accurately predicted using Hayat dead-space model applied to a linearly graded junction doping profile.

Dopant profiling in silicon nanowires measured by scanning capacitance microscopy

AbstractSilicon nanowires (SiNWs) with axial doping junctions were synthesized via the Au‐catalyzed vapor–liquid–solid growth method with the use of HCl. In this work, dopant profiling from three axially doped SiNWs with p–i, p–n and n–i–p junctions were investigated using both scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). It turns out that observed doping contrasts in SEM are also affected by the surface roughness and sample charging. In contrast, SCM allows us to delineate with sub‐10 nm resolution the electrical junctions and provides a relative value of the doping concentration in each segment of the NW. SCM clearly evidences the expected doping regions within these SiNWs thanks to the addition of HCl during the growth that strongly prevents shell overgrowth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Source Doping Profile Design for Si and Ge Tunnel FET

The source junction doping profile design for Si and Ge tunnel FET (TFET) is discussed and compared in this paper. By using Sentaurus TCAD tools with calibrated dynamic non-local band-to-band tunneling and non-local trap-assisted-tunneling models, it is shown that when Si TFET’s source doping gradient increases from 1.5 to 15 nm/dec, due to the gradual band bending and lower electric field at tunnel junction, average subthreshold slope (SS) increases from 38 to 64 mV/dec, onset voltage increases by 0.1 V and ON-current decreases by almost one decade. Although Ge TFET has larger tunneling electric field, the doping profile impact on SS is more severe than that of Si TFET. The design margin for doping profile under different gate length, gate oxide thickness and source-gate overlap is also discussed. Results show that for short channel Si TFETs, doping profile design margin for SS below 60mV/dec decreases as gate length shortens. For short channel Si TFETs design, the process requirement of abrupt source doping profile can be relaxed if thin gate oxide and a small underlap at the source junction are employed, and more stringent process control is required for Ge TFETs.

High-Speed and Low-Power Ultradeep-Submicrometer III-V Heterojunctionless Tunnel Field-Effect Transistor

Tunnel field-effect transistor (TFET) devices are gaining attention because of good scalability and they have very low leakage current. However, they suffer from low ON-current and high threshold voltage. In this paper, we present III-V heterojunctionless TFET (H-JLTFET) for circuit applications. This paper elaborates on interfacing of III-V with group IV semiconductors for heterojunction. Implementing heterojunction and bandgap engineering, we found that devices have significantly improved performance with very high speed even at very low operating voltage. As there is no doping junction present, future scaling could be feasible along with much higher speed of charge carriers than in silicon. GaAs:Si, Si:Si0.3Ge0.7, Si:InAs, and GaAs:Ge, H-JLTFET interface for 20-nm gate length (EOT=2 nm) and dielectric, HfO2 at VGS=1 V and temperature of 300 K have ION of 0.02-12.5 mA/μm, ION/IOFF of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> -10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> , and subthreshold swing (average) of 16-74 mV/decade.

Research of a New Type of Solar Cell Materials

Solar energy is the inexhaustible,enewable Energy. The solar cell is the solar light energy into electricity. The unique advantages of solar cell. Potential, more than wind, hydro, geothermal energy, nuclear energy and other resources, is expected to become the main pillar of power supply in the future. This paper studies that the main parameters of monocrystalline crystal silicon solar battery: the junction depth and superficial concentrations influence on electrical characteristics of monocrystalline silicon solar battery. The result shows that for maximum efficiency, it is bound to get the largest possible open circuit voltage, short circuit current and fill factor of the product, therefore, it is necessary to control these two parameters, the junction depth and doping parameters. If the junction depth is constant, with the increased superficial doping concentration of monocrystalline silicon solar battery, the photoelectric conversion efficiency of the battery increases slowly at first and then rapidly decreases, and the deeper the junction depth is, the more obvious trend of the photoelectric conversion efficiency is.

Variations in junction capacitance and doping activation associated with electrical stress of InGaN/GaN laser diodes

This paper presents a study of the effects of combined electrical and thermal stress tests on commercially-available InGaN-based blue laser diodes. By means of electrical and optical measurements, we have found that stress has two major consequences: (i) an initial decrease in threshold current, which is ascribed to the increase in the activation of p-type dopant, and (ii) a subsequent increase in threshold current, which – based on optical and electrical characterization – is ascribed to the generation/propagation of non-radiative defects within the active region of the devices.

Characteristics of fast ions from laser-induced plasma and their applicability to shallow junction doping

The characteristics of fast ions generated from laser-induced plasma on a boron solid target have been studied for an application to shallow junction doping. The peak position in the produced B ion energy spectra can be controlled in a 150–550eV range by changing the laser intensity. From the measurement of B ion energy spectrum which was resolved into charge states at several laser intensities, most part of the energy spectra around the peak position was found to be composed of B+ ions at the laser intensity less than 3.0×1010W/cm2. The number of produced ions around the peak of the energy spectrum was about 2×1012ions/(eV·Sr) or higher within the emission angle smaller than 45°. These results indicate that the produced B+ ions are applicable to shallow doping in a sub-10nm range.

Rectification Effects of ZnO-Based Transparent Nanodiodes on Glass and Flexible Plastic Substrates

Self-switching nanodiodes (SSDs) using zinc oxide (ZnO) were fabricated on glass substrates. The SSDs using ZnO have attracted significant attention as transparent devices because of their low cost, abundance in nature, and so on. Rectification characteristics in the SSDs were resemblance to the characteristics of conventional diodes with use of a doping junction or a barrier structure. The changes in characteristics depending on the shape of SSDs were investigated. Channel widths in the SSD of 230 and 190 nm and turn-on voltages of 5 and 8 V were obtained. On the other hand, it was found that the channel length influences the current strength. Moreover, after coating the devices with HfO2 to enhance the electric field coupling, the rectification behavior was maintained while the device current increased dramatically. The SSDs were fabricated using ZnO on flexible plastic substrates. For channel widths of 250 and 200 nm, turn-on voltages of 4 and 6 V were obtained, respectively. We also obtained clear rectification and observed the dependence of the turn-on voltage on the channel width.

Spatially Resolved Correlation of Active and Total Doping Concentrations in VLS Grown Nanowires

Controlling axial and radial dopant profiles in nanowires is of utmost importance for NW-based devices, as the formation of tightly controlled electrical junctions is crucial for optimization of device performance. Recently, inhomogeneous dopant profiles have been observed in vapor–liquid–solid grown nanowires, but the underlying mechanisms that produce these inhomogeneities have not been completely characterized. In this work, P-doping profiles of axially modulation-doped Si nanowires were studied using nanoprobe scanning Auger microscopy and Kelvin probe force microscopy in order to distinguish between vapor–liquid–solid doping and the vapor–solid doping. We find that both mechanisms result in radially inhomogeneous doping, specifically, a lightly doped core surrounded by a heavily doped shell structure. Careful design of dopant modulation enables the contributions of the two mechanisms to be distinguished, revealing a surprisingly strong reservoir effect that significantly broadens the axial doping junctions.

Field-effect piezoresistors for vibration detection of nanobeams by using monolithically integrated MOS capacitors

A novel piezoresistive sensing method is presented herein for the detection of nanobeam resonator based on a monolithically integrated MOS (metal–oxide–semiconductor) capacitor structure. The bottom layer of the nanobeam located beneath the MOS capacitor is utilized as a piezoresistor for the detection of internal stress resulting from nanobeam deformation, and therefore the challenging process of ultra-shallow junction doping is avoided. When a bias voltage applied on the MOS gate exceeds the threshold, the depletion layer width is built up to the maximum, and the piezoresistive cancellation effect beside the neutral plane is eliminated. Based on a conventional microelectromechanical (MEMS) process, an MOS capacitor is fabricated at the terminal of a double-clamped nanobeam with dimensions of 46 µm × 7 µm × 149 nm. The measured R–V curve of this MOS structure presents a 64.7 nm thick piezoresistor which closely agrees with the design. This double-clamped nanobeam is excited into mechanical resonance by mounting it on a piezoelectric ceramic, and the amplitude–frequency response is measured by a network analyzer. The measured resonant frequency is 3.97 MHz and the quality (Q)-factor is 82 in atmosphere environment. Besides, this piezoresistive sensing method is verified by a laser-Doppler vibrometry.

Systematic optimization of quantum junction colloidal quantum dot solar cells

The recently reported quantum junction architecture represents a promising approach to building a rectifying photovoltaic device that employs colloidal quantum dot layers on each side of the p-n junction. Here, we report an optimized quantum junction solar cell that leverages an improved aluminum zinc oxide electrode for a stable contact to the n-side of the quantum junction and silver doping of the p-layer that greatly enhances the photocurrent by expanding the depletion region in the n-side of the device. These improvements result in greater stability and a power conversion efficiency of 6.1% under AM1.5 simulated solar illumination.

An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures

Silicon nanowire and nanopore arrays promise to reduce manufacturing costs and increase the power conversion efficiency of photovoltaic devices. So far, however, photovoltaic cells based on nanostructured silicon exhibit lower power conversion efficiencies than conventional cells due to the enhanced photocarrier recombination associated with the nanostructures. Here, we identify and separately measure surface recombination and Auger recombination in wafer-based nanostructured silicon solar cells. By identifying the regimes of junction doping concentration in which each mechanism dominates, we were able to design and fabricate an independently confirmed 18.2%-efficient nanostructured 'black-silicon' cell that does not need the antireflection coating layer(s) normally required to reach a comparable performance level. Our results suggest design rules for efficient high-surface-area solar cells with nano- and microstructured semiconductor absorbers.

Rectifying characteristics of thin film self-switching devices with ZnO deposited by atomic layer deposition

To realise a rectifying device utilising ZnO, self-switching devices (SSDs) have been fabricated using ZnO thin films. The SSDs do not require a p-type doping junction or a Schottky barrier. At first, normally-off ZnO thin film transistors were fabricated, which exhibited control of threshold voltage by the channel length. Thin film SSDs using a thin film transistor structure were successfully fabricated by connecting the gate electrode with the source electrode. Finally, half-wave rectification using thin film SSDs is demonstrated, which reveals the possibility of ZnO thin film SSDs for power supply.

4H-SiC P&lt;sup&gt;+&lt;/sup&gt;N UV Photodiodes : A Comparison between Beam and Plasma Doping Processes

This paper presents a study of 4H-SiC UV photodetectors based on p+n thin junctions. Two kinds of p+ layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and the subsequent annealing) on the device characteristics. Aluminum and Boron dopants have been introduced by beam line and by plasma ion implantation, respectively. Dark currents are lower with Al-implanted diodes (2 pA/cm2 @ - 5 V). Accordingly to simulation results concerning the influence of the junction thickness and doping, plasma B-implanted diodes give rise to the best sensitivity values (1.5x10-1 A/W @ 330 nm).

Enhanced optical bistability from self-heating due to free carrier absorption in substrate removed silicon ring modulators

We show enhanced optical bistability induced by free carrier absorption from junction doping in substrate-removed silicon ring modulators. Such linear thermal effects dominate the loss in high-speed depletion silicon ring modulators. Optical bistability was observed with about 100 μW of input optical power. We further show that such thermal interactions causes data-dependent ring resonance shifts, and consequently severely degrade the data modulation quality at low speeds. The frequency response of this effect was measured to be about 100~200 kHz.

Surface Potential Measurements of Reconfigurable p-n Junctions in Graphene

The direct surface potential measurement of reconfigurable graphene p-n junctions in exfoliated graphene deposited on a buried split-gate test structure is reported. The experimental geometry permitted direct imaging of the Fermi level variation across the electrostatically-doped p-n junction using Kelvin Probe Force Microscopy (KPFM). The measured graphene p-n junction doping profile and junction width are in good agreement with predictions from finite-element calculations.

A study on the performance of metal-oxide-semiconductor-field-effect-transistors with asymmetric junction doping structure

Diode currents of MOSFET were studied and characterized in detail for the ion implanted pn junction of short channel MOSFETs with shallow drain junction doping structure. The diode current in MOSFET junctions was analyzed on the point of view of the gate-induced-drain leakage (GIDL) current. We could found the GIDL current is generated by the band-to-band tunneling (BTBT) of electrons through the reverse biased channel-to-drain junction and had good agreement with BTBT equation. The effect of the lateral electric field on the GIDL current according to the body bias voltage is characterized and discussed. We measured the electrical doping profiling of MOSFETs with a short gate length, ultra thin oxide thickness and asymmetric doped drain structure and checked the profile had good agreement with simulation result. An accurate effective mobility of an asymmetric source–drain junction transistor was successfully extracted by using the split C–V technique.

Research of Electric Properties of Monocrystalline Silicon Solar Battery

With crystalline silicon solar battery industry is developing rapidly, there are scientific significance and application value for guiding the industrial production using analysis of the electrical properties of crystalline silicon solar battery. This paper studies that the main parameters of monocrystalline crystal silicon solar battery: the junction depth and superficial concentrations influence on electrical characteristics of monocrystalline silicon solar battery. The result shows that for maximum efficiency, it is bound to get the largest possible open circuit voltage, short circuit current and fill factor of the product, therefore, it is necessary to control the junction depth and doping parameters. If the junction depth is constant, with the increased superficial doping concentration of monocrystalline silicon solar battery, the photoelectric conversion efficiency of the battery increases slowly at first and then rapidly decreases, and the deeper the junction depth is, the more obvious trend of the photoelectric conversion efficiency is. If the superficial doping concentration is constant, the photoelectric conversion efficiency of the battery is increased with the reductive junction depth of surface of monocrystalline silicon solar battery.

Extraction of correct Schottky barrier height of sulfur implanted NiSi/n-Si junctions: Junction doping rather than barrier height lowering

Proper analysis of the Schottky barrier height extraction methods shows that sulfur implantation followed by anneal does not effectively reduce the Schottky barrier height of NiSi/n-Si contacts. Instead, the results for sulfur implanted samples are consistent with enhanced field emission due to an increased doping density of the surface region of the silicon. Sulfur has a large impact on contact resistivity for silicon with low initial doping concentration (&amp;lt;∼1017 cm−3), but little impact for silicon with high initial doping density (&amp;gt;∼1017 cm−3). Internal photoemission measurements show that the Schottky barrier height remains unchanged with sulfur implantation.

Gate-induced drain leakage in FD-SOI devices: What the TFET teaches us about the MOSFET

This paper compares the gate-induced drain leakage (GIDL) in fully-depleted (FD) silicon-on-insulator (SOI) tunneling field effect transistor (TFET) and in standard metal-oxide-semiconductor FET (MOSFET) fabricated in the same process. The measurements show that the MOSFET GIDL current is lower than the GIDL in a TFET with the same junction doping, especially for devices with thick gate oxide and under low drain bias. A model describing lateral band-to-band tunneling (BTBT) is developed for GIDL in the FD-SOI TFET. By combining the model of gate-controllable tunneling diode in series with a field effect diode, we achieve an accurate picture of GIDL in FD-SOI MOSFETs.