P-type Devices Research Articles

Charge Collection Studies and Electrical Measurements of Heavily Irradiated 3D Double-Sided Sensors and Comparison to Planar Strip Detectors

Three-dimensional (3D) silicon detectors offer advantages over standard planar devices as more radiation hard sensors. These detectors and their applications in the upgrades of the LHC experiments are discussed. 3D detectors with a double-sided geometry have been fabricated as very short strip detectors with similar inter-column spacing as proposed for the ATLAS pixel detector and LHCb vertex locator upgrades. The detectors have been irradiated up to a fluence of 2 × 1016 cm-2 1 MeV equivalent neutrons, which is twice the expected dose of the inner pixel layer of the ATLAS detector and of the upgraded LHCb vertex locator for LHC high luminosity upgrade (HL-LHC) operation. Electrical measurements show a lateral depletion voltage of only 4 V for the device before irradiation which increases to 200 V after an irradiation to a fluence of 1 × 1016 cm-2 1 MeV equivalent neutrons. The strip isolation of the p-type detectors was robust to the maximum fluence. Charge collection studies have been performed with analogue readout with 25 ns shaping time, as required for LHC experiments. The response of the detectors to high energy electrons from a 90Sr source and a collimated pulsed laser light source are shown and compared with planar devices. The 3D detector, operated at no more than 350 V, is shown to have superior charge collection characteristics to planar devices for all the fluence range expected at HL-LHC even when compared to planar devices operating at 1000 V. When operated at a bias voltage of 350 V the 3D detector collects 2.8 times more charge than a p-type planar device operated at 1000 V after a fluence of 1016 cm-2 1 MeV equivalent neutrons. Charge multiplication in 3D detectors is also reported, in both 90Sr and laser tests, which leads to further enhancement in the charge collection and signal-to-noise ratio of the detector. The effect is demonstrated, through laser tests, to occur close to the junction electrode.

Intrinsic reduction of ballistic hole current due to quantum mechanical coupling of heavy and light holes in p-type Si nanowire field effect transistors

Rigorous quantum mechanical transport calculations based on the multi-band k · p Hamiltonian are performed in this work to show that the coupling of heavy and light holes (LHs) greatly reduces on-state hole current in ultra-scaled p-type Si nanowire FETs. If the coupling between the heavy and light holes is artificially suppressed, on-current of the p-type devices almost doubles and becomes comparable to that of n-type counterparts. It is found that the effect of the coupling on the hole transport is maximized at the channel width of around 5 nm.

High-Gain Fully Printed Organic Complementary Circuits on Flexible Plastic Foils

We present several fully printed organic complementary circuits using n- and p-type organic thin-film transistors. n-Type and p-type devices are developed on a flexible polyethylene-naphthalate substrate. All organic layers are deposited using a low-cost screen-printing technique. The inverters show a high gain and a switching point at exactly VDD/2. A seven-stage voltage-controlled oscillator (VCO) is designed with an organic output buffer, using the n- and p-type organic transistors. This VCO oscillates at a frequency of 186 Hz. Finally, two complementary differential amplifiers with high gain and large bandwidth are presented. The amplifiers only draw a 1-μA current from a 40-V power supply.

Spectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystals

3′-methyl-(5,5′′-bis[3-ethyl-3-(6-phenyl-hexyloxymethyl)-oxetane])-2,2′:5′,2′′-terthiophene (5T(Me)Ox) is a solution processable small molecule semiconductor displaying smectic-C and nematic liquid crystal phases. The pendant oxetane group can be polymerized in situ in the presence of a suitable photoacid at concentrations ≥1% by weight. Spin-coated films of pure 5T(Me)Ox and 5T(Me)Ox doped with the soluble photoacid were characterized by absorption and photoluminescent spectroscopy. Thick pristine films showed absorption and emission from a crystalline phase. Thin monolayer (<5 nm) films, as well as thicker photoacid doped films, instead showed absorption from an H-aggregate phase and emission from an excimer. Optical microscopy showed a significant change in film structure upon addition of the photoacid; large and well-orientated crystals being replaced by much smaller domains which appear to vary in thickness. Grazing Incidence Wide Angle X-Ray Scattering (GIWAXS) was used to characterize the packing and orientation of molecules in the crystalline and doped samples. The results are consistent with the photoacid doped samples forming layers of H-aggregate phase monolayer sheets parallel to the substrate where the photoacid inhibits the transition into the three-dimensionally ordered crystalline phase. Field-effect transistors and light emitting diodes were constructed incorporating 5T(Me)Ox as the active layer. Pure 5T(Me)Ox field-effect transistors showed good, p-type device characteristics, but the morphological changes upon doping result in a loss of transistor action. In the diodes, curing through melting and exposure to UV light followed by photoacid removal resulted in an increase in current density but a decrease in light emission. These results indicate that the presence of the photoacid (≥1% by weight) can have a dramatic effect on the structure, morphology and device performance of ordered, photopatternable materials for organic electronics.

Resistively Detected Nuclear Magnetic Resonance in n- and p-Type GaAs Quantum Point Contacts

We present resistively detected NMR measurements in induced and modulation-doped electron quantum point contacts, as well as induced hole quantum point contacts. While the magnitude of the resistance change and associated NMR peaks in n-type devices is in line with other recent measurements using this technique, the effect in p-type devices is too small to measure. This suggests that the hyperfine coupling between holes and nuclei in this type of device is much smaller than the electron hyperfine coupling, which could have implications in quantum information processing.

CMOS Inverter Based on Schottky Source–Drain MOS Technology With Low-Temperature Dopant Segregation

This letter demonstrates the integration of complementary dopant-segregated Schottky barrier MOSFETs into CMOS inverters. The implementation of a valence-band-edge silicide, namely, PtSi, associated to arsenic (As) and boron (B) low-temperature segregation is validated for the first time at the circuit level. Current drives for n- and p-type devices are Ion = 596/378 μA/μm at Vds = |1.1 V| and |Vgs| = 2 V to account for the 2.4-nm gate oxide thickness. Excellent inverter voltage transfer characteristics, large voltage gain, and appreciable noise margins have been obtained down to 0.5 V of supply voltage.

Time-Dependent Dielectric Breakdown and Stress-Induced Leakage Current Characteristics of 0.7-nm-EOT $\hbox{HfO}_{2}$ pFETs

In this paper, we examine the time-dependent dielectric breakdown (TDDB) reliability of p-type field-effect transistor devices with 0.7-nm-equivalent-oxide-thickness HfO2 gate dielectric layers. The TDDB distributions indicate ten-year lifetime with operating voltages in excess of 1 V. The reason for this high reliability lies in the high Weibull slopes (~1.2) of the measured TDDB distributions. In order to understand the mechanism behind the high Weibull slope, a detailed study of the defect generation by stress-induced leakage current (SILC) measurements is presented. The layers show different defect generation behavior as a function of temperature where the SILC generation rate at high temperature is stress voltage dependent.

Midinfrared photoresponse of Ge quantum dots on a strained Si0.65Ge0.35 layer

We report on intraband photocurrent spectroscopy of Ge self-assembled quantum dots placed on a strained Si0.65Ge0.35 quantum well, which, in turn, is incorporated in a Si matrix. The p-type devices show broad spectral response ranging from 2 to 12 µm. By a comparison between photocurrent measurements and the hole energy level scheme, as deduced from six-band k ⋅ p calculations, the two main contributions to the photoresponse are identified. The absorption band between 2 and 4 µm is attributed to the bound-to-continuum transitions between the bound states of the quantum dots and the continuum states in the Si barrier. The photoresponse at longer wavelength (4–12 µm) is associated with hole transitions from the dots to the nearby Si0.65Ge0.35 layer.

Ambipolar copper phthalocyanine transistors with carbon nanotube array electrodes

We report on organic thin film transistors (OTFTs) based on copper phthalocyanine (CuPc) having electrodes consisting of isolated carbon nanotube (CNT) arrays embedded in the organic layer. CuPc OTFT with CNT array electrodes show p-type behavior with Ohmic hole injection, high hole mobility, and enhanced switching characteristics at low voltage. The p-type devices are converted to ambipolar OTFT by vacuum annealing. Despite the large offset between the CNT work function and the CuPc energy levels, electron injection characteristics are also Ohmic. The extension of CNT electrodes to the phthalocyanine family confirms the validity of this contact approach for organic electronic devices.

Efficient CNTFET-based Ternary Full Adder Cells for Nanoelectronics

This paper presents two new efficient ternary Full Adder cells for nanoelectronics. These CNTFET-based ternary Full Adders are designed based on the unique characteristics of the CNTFET device, such as the capability of setting the desired threshold voltages by adopting proper diameters for the nanotubes as well as the same carrier mobilities for the N-type and P-type devices. These characteristics of CNTFETs make them very suitable for designing high-performance multiple-Vth structures. The proposed structures reduce the number of the transistors considerably and have very high driving capability. The presented ternary Full Adders are simulated using Synopsys HSPICE with 32 nm CNTFET technology to evaluate their performance and to confirm their correct operation.

Air-Stable Conversion of Separated Carbon Nanotube Thin-Film Transistors from p-Type to n-Type Using Atomic Layer Deposition of High-κ Oxide and Its Application in CMOS Logic Circuits

Due to extraordinary electrical properties, preseparated, high purity semiconducting carbon nanotubes hold great potential for thin-film transistors (TFTs) and integrated circuit applications. One of the main challenges it still faces is the fabrication of air-stable n-type nanotube TFTs with industry-compatible techniques. Here in this paper, we report a novel and highly reliable method of converting the as-made p-type TFTs using preseparated semiconducting nanotubes into air-stable n-type transistors by adding a high-κ oxide passivation layer using atomic layer deposition (ALD). The n-type devices exhibit symmetric electrical performance compared with the p-type devices in terms of on-current, on/off ratio, and device mobility. Various factors affecting the conversion process, including ALD temperature, metal contact material, and channel length, have also been systematically studied by a series of designed experiments. A complementary metal-oxide-semiconductor (CMOS) inverter with rail-to-rail output, symmetric input/output behavior, and large noise margin has been further demonstrated. The excellent performance gives us the feasibility of cascading multiple stages of logic blocks and larger scale integration. Our approach can serve as the critical foundation for future nanotube-based thin-film macroelectronics.

Efficient CNTFET-based Ternary Full Adder Cells for Nanoelectronics

Abstract This paper presents two new efficient ternary Full Adder cells for nanoelectronics. These CNTFET-based ternary Full Adders are designed based on the unique characteristics of the CNTFET device, such as the capability of setting the desired threshold voltages by adopting proper diameters for the nanotubes as well as the same carrier mobilities for the N-type and P-type devices. These characteristics of CNTFETs make them very suitable for designing high-performance multiple-V th structures. The proposed structures reduce the number of the transistors considerably and have very high driving capability. The presented ternary Full Adders are simulated using Synopsys HSPICE with 32 nm CNTFET technology to evaluate their performance and to confirm their correct operation.

An Efficient Gate Library for Ambipolar CNTFET Logic

Recently, several emerging technologies have been reported as potential candidates for controllable ambipolar devices. Controllable ambipolarity is a desirable property that enables the on-line configurability of n-type and p-type device polarity. In this paper, we introduce a new design methodology for logic gates based on controllable ambipolar devices, with an emphasis on carbon nanotubes as the candidate technology. Our technique results in ambipolar gates with a higher expressive power than conventional complementary metal-oxidesemiconductor (CMOS) libraries. We propose a library of static ambipolar carbon nanotube field effect transistor (CNTFET) gates based on generalized NOR-NAND-AOI-OAI primitives, which efficiently implements XOR-based functions. Technology mapping of several multi-level logic benchmarks that extensively use the XOR function, including multipliers, adders, and linear circuits, with ambipolar CNTFET logic gates indicates that on average, it is possible to reduce the number of logic levels by 42%, the delay by 26%, and the power consumption by 32%, resulting in a energy-delay-product (EDP) reduction of 59 % over the same circuits mapped with unipolar CNTFET logic gates. Based on the projections in [1], where it is stated that defectfree CNTFETs will provide a 5x performance improvement over metal-oxide-semiconductor field effect transistors, the ambipolar library provides a performance improvement of 7x, a 57% reduction in power consumption, and a 20x improvement in EDP over the CMOS library.

A systematic study of (NH4)2S passivation (22%, 10%, 5%, or 1%) on the interface properties of the Al2O3/In0.53Ga0.47As/InP system for n-type and p-type In0.53Ga0.47As epitaxial layers

In this work, we present the results of an investigation into the effectiveness of varying ammonium sulphide (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 min at 295 K, immediately prior to atomic layer deposition of Al2O3. Multi-frequency capacitance-voltage (C-V) results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n-type and p-type devices treated with the 10%(NH4)2S solution. The deleterious effect on device behavior of increased ambient exposure time after removal from 10%(NH4)2S solution is also presented. Estimations of the interface state defect density (Dit) for the optimum 10%(NH4)2S passivated In0.53Ga0.47As devices extracted using an approximation to the conductance method, and also extracted using the temperature-modified high-low frequency C-V method, indicate that the same defect is present over n-type and p-type devices having an integrated Dit of ∼2.5×1012 cm−2 (±1×1012 cm−2) with the peak density positioned in the middle of the In0.53Ga0.47As band gap at approximately 0.37 eV (±0.03 eV) from the valence band edge. Both methods used for extracting Dit show very good agreement, providing evidence to support that the conductance method can be applied to devices incorporating high-k oxides on In0.53Ga0.47As.

High hole mobility of 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene in field effect transistor

Triphenylamine-functionalized tetraphenylethene shows aggregation-induced emission feature with unity solid-state fluorescence efficiency. Its amorphous film can function in a p-type FET device with field effect mobility up to 2.6 × 10(-3) cm(2)/Vs.

Understanding the p-type defect chemistry of CuCrO2

CuCrO2 is the most promising Cu-based delafossite for p-type optoelectronic devices. Despite this, little is known about the p-type conduction mechanism of this material, with both CuI/CuII and CrIII/CrIV hole mechanisms being proposed. In this article we examine the electronic structure, thermodynamic stability and the p-type defect chemistry of this ternary compound using density functional theory with three different approaches to the exchange and correlation; the generalized-gradient-approximation of Perdew, Burke and Ernzerhof (PBE), PBE with an additional correction for on-site Coulombic interactions (PBE + U) and the nonlocal, screened-exchange hybrid functional HSE06. The fundamental band gap of CuCrO2 is demonstrated to be indirect in nature. Under all growth conditions, the dominant intrinsic p-type defect will be the Cu vacancy, with hole formation centered solely on the Cu sublattice. Mg doping is found to be significantly lower in energy than intrinsic defect formation, explaining the large increases in conductivity seen experimentally. Cu-rich/Cr-poor growth conditions are found to be optimal for both intrinsic and extrinsic (Mg doping) defect formation, and should be adopted to maximize performance.

(1 0 0) GaAs/AlxGa1−xAs heterostructures for Zeeman spin splitting studies of hole quantum wires

We have developed undoped (100) GaAs/Al0.34Ga0.66As heterostructures, in which a 2D hole system is introduced by a heavily carbon doped field effect gate. We compare transport and mobility data from these (100) undoped devices with conventional Si modulation doped p-type devices grown on (311) substrates. Finally we present conductance quantization data for hole quantum wires made of these (100) heterostructures.

Evidence of Responsivity and Breakdown Voltage Improvement in SiCGe/SiC Phototransistor with Charge Compensation Layer

An n-SiC/p-SiCGe/n-SiCGe heterojunction phototransistor with charge compensation layer has been simulated with commercial simulator MEDICI. With wide bandgap SiC emitter and p-type SiCGe charge-compensation layer, device responsivity and breakdown voltage has been improved. It is found that with p-type SiCGe layer, the responsivity is nearly two times of without one. Furthermore, flat electrical field distribution during off-state enable it supports higher reverse bias, thus breakdown voltage increased from 450V to 580V for the given structure, and both breakdown voltage and responsivity increase with light absorption region length.

Extraction of low-frequency noise in contact resistance of organic field-effect transistors

The power spectral density of low-frequency noise in contact resistance, SRsd, of organic transistors is evaluated by the transfer-line method. The obtained gate-voltage dependent SRsd is then normalized by the square of contact resistance, which is extracted from dc current-voltage (I-V) measurements. After normalization, slightly variable and nearly constant SRsd/Rsd2 with respect to gate voltage are obtained in the range 10−7–10−6 μm/Hz at 20 Hz in p-type and n-type devices, respectively. This method proves suitable to investigate separately the origin of the noise sources in channel as well as in contact region.

Small-signal analysis of high-performance p- and n-type SOI SB-MOSFETs with dopant segregation

In this paper, we present fully-depleted Schottky barrier MOSFETs with dopant-segregated NiSi source and drain junctions. Schottky barrier MOSFETs with a channel length of 80 nm show high on-currents of 900 μA/μm for n-type devices with As segregation at V gs − V t = 3 V and V ds = 1.2 V and 427 μA/μm for p-type devices with B segregation at V gs − V t = −2.8 V and V ds = −1.2 V. A detailed high-frequency characterization proves the high-performance of the devices with cut-off frequencies f T of 117 GHz for n-type and 63 GHz for p-type Schottky barrier MOSFETs and clearly elucidates the effects of extrinsic and intrinsic device parameters as a function of the gate length.