PNP Bipolar Transistors Research Articles

Response Mechanisms of Additional Displacement Defects in Oxides to Ionization Damage in Bipolar Transistors

When evaluating the radiation damage of charged particles to bipolar junction transistors (BJTs), the additional displacement defects caused by charged particles in oxide cannot be ignored. In this paper, we demonstrate that the additional displacement defects can enhance or weaken the ionization damage level of BJTs. Additional displacement defects always weaken ionization damage in PNP BJTs and may enhance it in NPN BJTs. In addition, in the same BJTs, the response of additional displacement defects in oxide at different depths to ionization damage is also different, which strongly depends on the depth of additional displacement defects. Additional displacement defects in oxide show different results in response to ionization damage in different types of BJTs, which brings complexity to the accurate assessment of radiation hardness of BJTs. Therefore, in this paper, three different types of BJTs are analyzed in detail. In their oxides, the response mechanism of additional displacement defects to ionization damage is analyzed in detail, which provides a reference for improving the evaluation accuracy of more types of BJTs.

To define nonradiative defects in semiconductors: An accurate DLTS simulation based on first-principle

Deep level transient spectroscopy (DLTS) is a crucial technique to characterize the defects in semiconductor devices. Within the framework of the state-of-the-art density functional theory (DFT), the simulation for experimental DLTS spectra is realized successfully with high accuracy and intrinsic physics in this work, of which the reliability is confirmed by nonlocal hybrid functional. The electron–phonon coupling is included to describe the thermal-activated behavior of the hot carrier nonradiative capture reflected by DLTS signal. In the case study, the divacancy in silicon is employed for the flow of DLTS calculation as a benchmark, of which the results are verified by our 40 MeV Si irradiation experiments on the NPN and PNP bipolar junction transistors and previous reports. The problem we can address is the identification of defect characterized in DLTS experiments. The realization of DLTS simulation would have a profound significance for understanding the underlying physics in experimental observations and be a powerful leverage to define defect nature in semiconductors.

BJT induced dark current in CMOS image sensors

This paper demonstrates that cut-off pnp Bipolar Junction Transistors (BJTs) can induce visible dark current to their nearby CMOS (Complementary Metal Oxide Semiconductor) image sensor pixels, supported with experimental results. Previously, it has been shown that active BJTs and forward-biased PN junctions can incur dark shading to nearby CMOS image sensor pixels through electroluminescence (EL). However, in our experiments, when the BJTs are in their cut-off region, they can induce dark current to nearby image pixels at a similar distance but the dark current level declines much faster. To figure out the causes of dark current induced by the cut-off BJTs, the thermal coefficient of their nearby image pixels has been measured and the current is found to double for every 5 °C temperature rise. This indicates the cut-off BJT induced dark current is mainly due to the diffusion current generated from the silicon neutral regions in the pinned photodiodes (PPDs). This is in contrast to the hot pixels’ dark current incurred by thermal generation, that doubles for every 10 °C increase in temperature, or EL that has a very small thermal coefficient.

A Thermally Stable Quasi-CMOS Bipolar Logic

Logic gates made of pairs of NPN and PNP bipolar transistors, similar to CMOS logic gates, have been proposed and patented long ago but did not find any practical application until now. Other bipolar technologies (TTL, TTL-S, ECL), once the technologies of choice for digital systems, were abandoned and superseded by CMOS. In this paper it is shown that now, when truly complementary pairs of bipolar transistors can be made, properly biased bipolar gates similar to CMOS gates are feasible, can be thermally stable and find practical applications.

GaN PNP light-emitting bipolar junction transistor

An light-emitting bipolar transistor (LEBJT) has been developed in response to aspirations for on-chip electronics with GaN-based light-emitting diode (LED) devices. The design utilizes the existing p-n junction of an LED structure to construct a PNP bipolar junction transistor comprising two back-to-back p-n junctions, saving the need for customized structures or epitaxial regrowth. Two designs of monolithic GaN LEBJTs have been demonstrated in this work—an LEBJT with a larger emitter area size for conversion of electronic to optical signal, as well as an LEBJT with reduced emitter area for boosting of current gain. Employing an emitter comprising an array of nanopillars patterned by nanosphere lithography, the LEBJT exhibits an average current gain of 20 and a bandwidth of 180 MHz.

Radiation effects of 50-MeV protons on PNP bipolar junction transistors

The effects of radiation on 3CG110 PNP bipolar junction transistors (BJTs) are characterized using 50-MeV protons, 40-MeV Si ions, and 1-MeV electrons. In this paper, electrical characteristics and deep level transient spectroscopy (DLTS) are utilized to analyze radiation defects induced by ionization and displacement damage. The experimental results show a degradation of the current gain and an increase in the types of radiation defect with increasing fluences of 50-MeV protons. Moreover, by comparing the types of damage caused by different radiation sources, the characteristics of the radiation defects induced by irradiation show that 50-MeV proton irradiation can produce both ionization and displacement defects in the 3CG110 PNP BJTs, in contrast to 40-MeV Si ions, which mainly generate displacement defects, and 1-MeV electrons, which mainly produce ionization defects. This work provides direct evidence of a synergistic effect between the ionization and displacement defects caused in PNP BJTs by 50-MeV protons.

Silicon-controlled Rectifier-based Electrostatic Discharge Protection Circuit with Additional NPN Parasitic Bipolar Junction Transistor for 5-V Application

This paper proposes a novel protection circuit based on a silicon-controlled rectifier (SCR) to prevent electrostatic discharge (ESD) at low voltages. The proposed device consists of an additional NPN parasitic bipolar transistor operated via application of an N+ diffusion region and a well breakdown voltage, to reduce the high trigger voltage caused by the well breakdown voltage of the existing SCR structure. Furthermore, the proposed device exhibits an improved trigger voltage, holding voltage, and dynamic resistance component when compared with existing parasitic PNP bipolar transistors. The proposed ESD protection circuit was manufactured using a 0.18 μm bipolar-CMOS-DMOS; it exhibited a significant improvement in electrical characteristics such as trigger voltage (8.1 V) and holding voltage (3.55 V), according to the results of transmission line pulse measurement. Hence, it is deemed to be suitable for 5-V-class applications.

Quantitative comprehension the impact of X-light on current gain of lateral PNP bipolar transistor

Bias emission voltage and dose-dependent current gain are the key parameters to detect the physical performance of bipolar transistors. Firstly, the effect of X-light with energy 22.1 and 25.0 keV from 109Cd on the current gain of lateral PNP bipolar transistors is measured. The substantial difference of current gain with the variation of bias and emission voltage is observed. Then, on basis of the outcomes of the nonlinear curve fitting approach, the relationship between bias voltage and emission-related current gain is successfully explained by using the model of combination Maxwell Boltzmann statistical with Bose-Einstein probability. The simulation results are in good agreement with the observed curves (current gain vs. voltage). The minimal correlation coefficient between experimental data and computed data is 0.998. In all cases considered, the mean relative error between the measured value and the model value is not more than 5.0%. Finally, the mathematical link between the parameters of current gain and voltage and the X-light dose is obtained. Therefore, using only one function, the current gain can be anticipated by the voltage and dose between bias and emission. The influence of X-light on the current gain of transverse PNP bipolar transistors is firstly discussed quantitatively.

Radiation mechanism of gate-controlled lateral PNP bipolar transistors in the hydrogen environment

Hydrogen plays a crucial role in realizing modern silicon devices. Molecular hydrogen may be found in processes of integrated circuit fabrication and packaging, such as wafer cleaning procedure, film depositions, high- and low-temperature anneal and die attachment by forming gas. It has been shown that hydrogen has strong effects on the total dose and dose rate response to bipolar devices. In order to study the relationship between hydrogen and radiation-induced products, we preform two experiments by using gate-lateral PNP transistors. In the first experiment, one set of devices is soaked in 100% hydrogen gas for 60 h and another set is not soaked, they are together irradiated at 5 rad(Si)/s to a total dose of 50 krad(Si). In the second experiment, devices are irradiated at 50 rad(Si)/s to 100 krad(Si), and then one group is annealed in 100% hydrogen gas and the other is annealed in the air for 40 h at the same temperature. The results show that the damage to devices which are soaked in hydrogen before irradiation is stronger than the devices that are not soaked, the anneal characteristics of devices in hydrogen gas are also changed more greatly than in the air. So the hydrogen can enhance the radiation and anneal damage to bipolar transistors. Using the gate-sweep technique, the radiation-induced products are separated and show that the hydrogen that enters into the transistor will cause the interface traps to increase and oxide trapped charge to decrease. The main reason is that the hydrogen can react with the oxide trapped charge to produce protons which can transport to the Si/SiO<sub>2</sub> interface, and then react with H-passivized bond to create interface trap. Based on the reaction mechanism presented in our work, a numerical model of enhanced low dose rate sensitivity including molecular hydrogen reaction and proton generation mechanism is established. The simulation results for the density of interface traps and oxide trapped charge show a trend consistent with the experimental data, which verifies the correctness of the damage mechanism. This research provides not only the basis of the study of damage mechanism of bipolar devices, but also the powerful support for hydrogen soaking irradiation acceleration method.

Quantitative study of the effect of gamma radiation on lateral PNP bipolar transistor

Bias-emission voltage and dose-dependent current gain is a key parameter in detecting the physical properties of the bipolar transistor. The first objective of this work is to measure the influences of gamma radiation on current gain in lateral PNP bipolar transistors. Substantial differences of the current gain as a function of voltage between bias and emission are observed. Then, based on the calculated results from the non-linear curve fitting method, the voltage between bias and emission-dependent current gain is theoretically explained successfully via the asymmetric peak function. The simulations agree very well with the observed curves (current gain versus voltage). The minimum correlation coefficient between the experimental and calculated data is 0.998. The average relative errors between the measured and modeled values do not exceed 9.14% in all considered cases. Finally, the mathematical relationships between the parameters, which serve to link the current gain and voltage together with dose, are obtained. Consequently, the current gain can be predicted by both voltage between bias and emission and dose using only one function. To the best knowledge of the author, the effects of gamma irradiation on the lateral PNP transistors are quantitatively discussed for the first time in current gain.

Laser Writable Multifunctional van der Waals Heterostructures.

Achieving multifunctional van der Waals nanoelectronic devices on one structure is essential for the integration of 2D materials; however, it involves complex architectural designs and manufacturing processes. Herein, a facile, fast, and versatile laser direct write micro/nanoprocessing to fabricate diode, NPN (PNP) bipolar junction transistor (BJT) simultaneously based on a pre-fabricated black phosphorus/molybdenum disulfide heterostructure is demonstrated. The PN junctions exhibit good diode rectification behavior. Due to different carrier concentrations of BP and MoS2 , the NPN BJT, with a narrower base width, renders better performance than the PNP BJT. Furthermore, the current gain can be modulated efficiently through laser writing tunable base width WB , which is consistent with the theoretical results. The maximum gain for NPN and PNP is found to be ≈41 (@WB ≈600nm) and ≈12 (@WB ≈600nm), respectively. In addition, this laser write processing technique also can be utilized to realize multifunctional WSe2 /MoS2 heterostructure device. The current work demonstrates a novel, cost-effective, and universal method to fabricate multifunctional nanoelectronic devices. The proposed approach exhibits promise for large-scale integrated circuits based on 2D heterostructures.

Temperature dependence of bipolar junction transistor current-voltage characteristics after low dose rate irradiation

Temperature variation on board can have a significant impact on electronic circuit parameters. In this paper, we investigate and model how both irradiated NPN and PNP-Bipolar Junction Transistors (BJTs) at room temperature respond electrically to temperature variation. A temperature-dependent analytical model for total-ionizing-dose-induced excess base current in BJTs is proposed. Our model captures base current dependence on temperature on irradiated parts. To do so, the devices under test are irradiated at room temperature with all terminals grounded. After irradiation, base currents are obtained, and the concentrations of oxide defects (i.e., oxide trapped charge and interface traps) created during irradiation are calculated. At the end, results from our analytical model and experimental data are compared to SPICE simulations. Both base current and defect densities resulting from room temperature irradiations are used as inputs to SPICE simulations and the analytical model. Experimental data obtained from measurements at both low and high temperatures on parts irradiated at room temperature are shown to compare well to the simulation results and analytical model over a range of temperatures. The modeling work shows that SPICE simulations can support qualification for commercial-off-the-shelf (COTS) linear bipolar components with temperature for space applications.

A Miniaturized 0.003 mm2 PNP-Based Thermal Sensor for Dense CPU Thermal Monitoring

Compact integrated thermal sensors are utilized to measure hot / cold spots in CPU cores in multiple locations and are important for the power/performance of the chip. Bipolar junction transistors (BJT) are the industry standard for temperature sensing elements because of their predictable physics. This paper reports on one of the smallest PNP BJT bandgap based thermal sensors to date. Miniaturization was achieved by using switched capacitor circuits with very small capacitors as opposed to the standard resistor-based bandgaps. Digitally controlled trims enable either a higher resolution or a nearly linear response to temperature. This ultra-miniature 0.003 mm2, PNP thermal- based sensor is fabricated in TSMC 65nm. It achieves a measured total ${\pm 3\sigma }$ error of ±1.35°C with a resolution of 65mK and a 4.1ms conversion time. The sensor is optimized for dense CPU thermal mapping.

A high-order curvature compensated voltage reference based on lateral BJT

This paper presents a curvature compensated voltage reference (VR), which is based on lateral PNP bipolar junction transistor (BJT). The proposed VR is fabricated in 0.18 μm CMOS process. The circuit consists of two first-order current-mode band gap references (BGR) and a subtraction circuit. Temperature characteristics of lateral PNP BJT is utilized for temperature curvature compensation. Moreover, in order to reduce the errors introduced by the conventional subtraction circuit, an improved subtraction circuit is proposed for improving performance of curvature compensation. Test results of prototype chips show the proposed VR has an average 2.36 ppm/° C within temperature range of −40 ° C to 120 °C. Power supply rejection ratio (PSRR) of the proposed VR achieves 69.5 dB at 100 Hz.

Bipolar Transistor Test Structures for Extracting Minority Carrier Lifetime in IGBTs

Vertical PNP bipolar transistor test structures were fabricated and measured, attempting to electrically obtain information on carrier lifetime in the voltage-supporting base region of Insulated Gate Bipolar Transistors (IGBTs). Owing to the structural similarity, the test structures and functional IGBTs can be integrated on the same wafers, making it possible to directly correlate lifetime data and IGBT characteristics. To solve a problem of leaky backside PN junction, common base current gain of the test devices was measured without applying a reverse bias between the collector and base terminals, which suppressed the leakage to an acceptable level. A simple analytical formula to convert the current gain to hole lifetime in the N-type base region was proposed and used, that takes into account the existence of a commonly used N-buffer layer adjacent to the backside P-collector layer. The validity of the formula was confirmed using TCAD simulations. This method was applied to IGBT wafers with two different wafer thicknesses (i.e., base lengths): $120~{{\mu }}\text{m}$ and $360~{{\mu }}\text{m}$ . Consistent lifetime values extracted in spite of the largely different thicknesses supports the validity of the proposed lifetime estimation method.

Gate Current and Snapback of 4H-SiC Thyristors on N+ Substrate for Power-Switching Applications

High-power switching applications, such as thyristor valves in a high-voltage direct current converter, can use 4H-SiC. The numerical simulation of the 4H-SiC devices requires specialized models and parameters. Here, we present a numerical simulation of the 4H-SiC thyristor on an N+ substrate gate current during the turn-on process. The base-emitter current of the PNP bipolar junction transistor (BJT) flow by adjusting the gate potential. This current eventually activated a regenerative action of the thyristor. The increase of the gate current from P+ anode to N+ gate also decreased the snapback voltage and forward voltage drop (Vf). When the doping concentration of the P-drift region increased, Vf decreased due to the reduced resistance of a low P-drift doping. An increase in the P buffer doping concentration increased Vf owing to enhanced recombination at the base of the NPN BJT. There is a tradeoff between the breakdown voltage and forward characteristics. The breakdown voltage is increased with a decrease in concentration, and an increase in drift layer thickness occurs due to the extended depletion region and reduced peak electric field.

Characteristics of displacement defects in PNP transistors caused by heavy ion irradiation

Characteristics of displacement defects in the 3CK3637 PNP bipolar junction transistors (BJTs) irradiated by 10 MeV Si, 40 MeV Si and 25 MeV C ions are investigated in this paper. Electrical parameters are measured in-situ using KEITHLEY a 4200-SCS semiconductor characterization system during irradiations. The radiation-induced defects caused by various ions for different displacement damage doses are characterized by deep level transient spectroscopy (DLTS). Experimental results show that the electrical degradation increases with increasing irradiation fluence. It is worth noting that the increase trend of the electrical degradation is different for the three types of ions. For the 10 MeV Si ions, the electrical degradation linearly increases, while, for the 40 MeV Si and 25 MeV C ions, the electrical degradation increases nonlinearly. The change in the reciprocal of current gain (Δ(1/β)) caused by 40 MeV Si and 25 MeV C ions can be normalized in one line at lower displacement damage doses. As the displacement damage dose increases to a certain threshold, the Δ(1/β) deviates from the normalized line. Based on the DLTS analyses, the dominant displacement defects in the 3CK3637 PNP BJTs irradiated by 40 MeV Si and 25 MeV C ions change with increasing displacement dose, leading to the existence of threshold in the electrical degradation curve.

Effects of pre-irradiated thermal treatment on ideal factor of excess base current in bipolar transistors

<sec>During the service of the spacecraft, it will be disturbed by the energetic particles and rays, and thus induce total ionizing dose (TID), displacement damage (DD) or single event effect (SEE) to generate inside the electronic system, which can seriously affect the service lifetime of the electronic components. The difference in structure and types of electronic components are less sensitive to the radiation effects, but bipolar transistor is strongly sensitive to ionizing radiation effect. As a basic component of bipolar circuits, the in-depth study of bipolar transistor ionization radiation effect is of significance for engineering.</sec><sec>It has been shown that the an amount of hydrogen can inevitably introduced from an external source during the sealing process of the devices. The KOVAR alloy is widely used as a metal cap material of bipolar transistor in the process of encapsulation. The residual gas analysis (RGA) for sealed Kovar lid packages is shown to have 1%–2% of the hydrogen in the cavity. The source of the hydrogen is generally considered to be out-gassing from the gold plating on the KOVAR. So far, the researches have focused on the study of the ionization damage effect of bipolar transistors with different structures under <sup>60</sup>Co gamma ray irradiation. There is lack of systemic study on the comparison of transistors packaged with and without cap.In this paper, we study the influence of sealed KOVAR lid packaged on ionizing radiation damage of lateral PNP bipolar transistor (LPNP) by using <sup>60</sup>Co gamma ray as an irradiation source. The semiconductor parameter analyzer is used to measure the electrical parameters of LPNP transistor during irradiation. The irradiation defects in LPNP transistors packaged with and without cap are characterized by deep level transient spectroscopy (DLTS). Experimental results show that the LPNP transistors packaged with and without cap have similar electrical characteristics. The base current increases with the total dose increasing, while the collector current remains almost constant. The degradation of LPNP transistor packaged with cap is more serious.</sec><sec>According to the excess base current varying with base-emitter voltage for the LPNP transistors packaged with and without cap, the degradation of bipolar transistor packaged with cap is more serious under the same irradiation conditions. According to the analysis of DLTS, comparing with bipolar transistor packaged without cap, the signal peak at about 300 K is shifted to the left for the bipolar transistor packaged with cap. These results indicate that the LPNP transistors packaged with cap can generate more interface states during irradiation, which is attributed to a large amount of hydrogen and water vapor out-gassing from the gold plating on the KOVAR, which is released under the thermal stress. In the sealed environment, hydrogen can only diffuse into the device cavity, and is combined with the metal material in the transistor to form metal hydride. Therefore the degradation of transistor is severe under the same irradiation condition.</sec>

Passive Impedance Matching for Implanted Brain–Electrode Interfaces

We propose a new technique for matching the high impedance of sub-cranial electrodes to wireless brain implants that is passive, highly tolerant of the dc offset voltage caused by the electrochemical reaction in the recording electrode, and complemented by an improved external interrogator design that exhibits reduced phase noise. As compared to previous wireless and batteryless brain implants, the proposed approach offers a remarkable improvement in sensitivity by 25 times. The proposed system consists of an external interrogator and a neuro-recorder implanted under the scalp. For operation, the interrogator sends a 2.4-GHz carrier signal to turn on the implant. This carrier self-biases a PNP Bipolar Junction Transistor (BJT) that enables matching to the recording electrode at frequency $f_{neuro}$ in a batteryless manner. Concurrently, the recorded neuropotentials (at frequency $f_{neuro}$ ) pass through a Schottky diode that allows them to mix with the carrier and generate a 4.8 $\text{GHz}\pm f_{neuro}$ modulated signal. The latter is then transmitted back to the interrogator for demodulation. To verify the implant's operation, in-vitro measurements are presented. Measurement results demonstrate that emulated neuropotentials as low as 200 $\mu V_{pp}$ can be detected at a 33- $\text{k}\Omega$ electrode impedance. As such, the proposed system presents a game-changing capability for a wide range of applications.

Impact of Electrical Stress on $\gamma$ Ray Irradiated Double Polysilicon Self-Aligned (DPSA) PNP Bipolar Transistors

Anomalous irradiation response to total ionizing dose effects of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co γ ray in double polysilicon selfaligned (DPSA) bipolar PNP transistors at a low dose rate was observed. It is experimentally revealed that the anomalous current gain (β) enhancement in Emitter-Base (E-B) forward-biased transistors during irradiation originates from a base current decrease. Based on the comparative forward high-current stress and forward-biased irradiation experimental results, the anomalous phenomenon can be ascribed to the atomic hydrogen electromigration and subsequent passivation of electronic interface traps located at the polysilicon grain boundaries and poly/monosilicon interfaces of DPSA's poly emitter contact layers. Although current gain enhancement occurs both in high-current stress and forward-biased irradiation stress PNP transistors, the physical mechanisms responsible for the variations are quite different. In the case of forward high-current stress, the damage mainly affects excessive base current of non-ideal components and decreases the emitter resistance. For forward-biased ionizing radiation stress, the damage not only induces both ideal and non-ideal components of the base current increase in the low bias region but also increases emitter resistance.