NPN Bipolar Transistors Research Articles

Experimental determination of intrinsic carrier density in 4H-SiC based on electron diffusion current in an npn bipolar junction transistor

The intrinsic carrier density of 4H-SiC at temperatures ranging from 294 to 595 K was derived by analyzing a collector current in an npn-type SiC bipolar junction transistor, the structure of which was designed based on a device simulation. The obtained intrinsic carrier density was in good agreement with the value calculated from the bandgap and effective densities of states taking multiple and non-parabolic SiC bands into account. The coincidence of the intrinsic carrier density obtained by these two different approaches indicates the usefulness of the proposed method and the validity of the evaluated value of intrinsic carrier density. The temperature dependence of the bandgap was also estimated from the deduced intrinsic carrier density and compared with an empirical formula. The derived bandgap agreed well with the empirical formula showing bandgap shrinkage at high temperatures. The errors in evaluating the intrinsic carrier density and the bandgap caused by the estimation of the hole density and electron mobility in the base layer are also discussed for the proposed method.

Silicon Nanowire Phototransistor Arrays for CMOS Image Sensor Applications.

This paper introduces a new design of silicon nanowire (Si NW) phototransistor (PT) arrays conceived explicitly for improved CMOS image sensor performance, and comprehensive numerical investigations clarify the characteristics of the proposed devices. Each unit within this array architecture features a top-layer vertical Si NW optimized for the maximal absorption of incoming light across the visible spectrum. This absorbed light generates carriers, efficiently injected into the emitter-base junction of an underlying npn bipolar junction transistor (BJT). This process induces proficient amplification of the output collector current. By meticulously adjusting the diameters of the NWs, the PTs are tailored to exhibit distinct absorption characteristics, thus delineating the visible spectrum's blue, green, and red regions. This specialization ensures enriched color fidelity, a sought-after trait in imaging devices. Notably, the synergetic combination of the Si NW and the BJT augments the electrical response under illumination, boasting a quantum efficiency exceeding 10. In addition, by refining parameters like the height of the NW and gradient doping depth, the proposed PTs deliver enhanced color purity and amplified output currents.

OPTICALLY PUMPED BIPOLAR TRANSISTOR

The properties of a bipolar npn transistor were studied when exposed to unmodulated incoherent radiation created by a “white” LED. The static and dynamic characteristics of the transistor were measured at various exposure intensities. It is shown that the change in the characteristics of the transistor under optical influence is due to an increase in the lifetime of nonequilibrium charge carriers and the photovoltaic effect in p-n junctions. For these reasons, the gain increases, the switching threshold decreases, and the transistor speed increases. The results obtained are applicable both to the creation of high-speed transistors and integrated circuits of a fundamentally new type.

High-Energy Radiation Effects on Silicon NPN Bipolar Transistor Electrical Performance: A Study with 1 MeV Proton Irradiation.

This study investigates the degradation of the silicon NPN transistor's emitter-base junction, specifically the 2N2219A model, under both forward and reverse polarization. We examine the current-voltage characteristics under the influence of 1 MeV proton irradiation at various fluencies, which are 5.3×108,5.3×1010,5×1011,5×1012, and 5×1013 protons/cm², all conducted at 307 K. The experimental findings elucidate a pronounced dependency of diode parameters, including the reverse saturation current, series resistance, and the non-idealist factor, on the incident proton flow. This observation underscores that proton-induced degradation is primarily driven by displacement damage, while recorded degradation is predominantly attributed to the generation of defects and interfacial traps within the transistor resulting from exposure to high-energy radiation. Our findings indicate that the effects of irradiation align more closely with the compensation phenomenon in doping rather than its reinforcement.

The design of a fully balanced current–tunable active RC integrator

The design of the active RC integrator presented in this research utilizes a fully balanced technique and current-tunable frequencies to create the active RC integrator and reliable circuit. The circuit is made up of six npn bipolar junction transistors (BJT), six resistors (R), and a capacitor (C), with the fully balanced technique used to make the circuit structure uncomplicated and symmetrical with signal differencing. This approach results in a low number of internal devices in the circuit, making it an attractive option for integrated circuit (IC) development. One of the key features of the fully balanced current-tunable active RC integrator is its ability to be frequency-tunable with bias current (If). This feature enables the circuit to be used in a variety of applications, including filter circuits, communication signal generators, instrumentation signal generators, and various automatic controls. The fully balanced design also ensures that the circuit is stable and robust, even in the presence of device parameter variations. To evaluate the performance of the active RC integrator, simulations were conducted using Pspice.
 The results show that a fully current-tunable active RC integrator can be precisely tuned with the active bias to a value consistent with the theoretically calculated value. This demonstrates the efficiency and reliability of the circuit design and simulation method. The Monte Carlo (MC) method was also used to analyze the circuit performance in cases where the resistor (R) and capacitor (C) device had a 10 percent error and the transistor gain (β) was set to an error of 50 percent. The MC analysis showed that the phase shift (degree) and magnitude (dB) of the circuit were stable, and the circuit's performance was not significantly impacted by the device parameter variations. This further demonstrates the robustness and versatility of the fully balanced current-tunable active RC integrator design. Finally, harmonic distortion was evaluated to confirm the performance of the designed and developed fully balanced current-tunable active RC integrator. The results showed low levels of harmonic distortion, which indicates that the circuit is suitable for high-performance applications that require low distortion

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.

Combined effects of total ionizing dose and electromagnetic pulse on a bipolar junction transistor

Bipolar Junction Transistors (BJTs) are widely used in the presence of ionizing radiation, such as in space or in the surroundings of nuclear reactors. For the application in these fields, the influence of Total Ionization Dose (TID) and Electromagnetic Pulse (EMP) on BJTs should be carefully considered. In this work, for the comprehension of the combined effects of TID and EMP on BJT, a numerical model of a NPN BJT (2N2222) is developed with the semiconductor device simulation software TCAD. The simulated results indicate that the TID of gamma-rays can increase the depletion layer area of the BJT and lead to a reduction of its current gain and that a negative base voltage may in these conditions cause the breakdown of the emitter junction. Therefore, the results obtained indicate that the combined TID and EMP can lower the breakdown voltage of the BJT.

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.

Research of single event burnout in a high-performance radiation-hardened SOI lateral power MOSFET

In this paper, a 60 V radiation-hardened SOI lateral power MOSFET (LDMOS) device is proposed and single event burnout (SEB) failure mechanism of the device is investigated by Sentaurus simulator. The SOI LDMOS device, with 2 μm drift region and extended N+ drain region, can achieve optimal breakdown voltage (BVDS, 67 V) and specific on-resistance (Ron,sp, 5 mΩ·cm2), while Ron,sp of the device without extended N+ drain is 5.6 mΩ·cm2. Sensitive region of the device for SEB is analyzed and the most sensitive region for SEB is near the center of drift region. The influence of different linear energy transfers (LETs) on SEB threshold voltage is explored and the device can survive at the full drain to source voltage (VDS) biasing of 60 V even for a highly-energetic ion with LET of 1 pC/μm (96 MeV·cm2/mg). Besides, heavily-doped P+ region is inserted on the source side and parameters of source region are optimized to improve SEB tolerance of the device. Second breakdown voltage of the device which correlates with SEB failure threshold is up to 66 V, indicating excellent SEB hardness of the device. Eventually, SEB failure mechanism of the device is investigated in detail and the action of the parasitic npn bipolar junction transistor (BJT) inherent in the device structure is the key to SEB tolerance of the device.

Simulation of Ionizing/Displacement Synergistic Effects on NPN Bipolar Transistors Irradiated by Mixed Neutrons and Gamma Rays

Transistors working in complex radiation environments such as space are simultaneously irradiated by neutrons and gamma rays. But the mechanism of the synergistic radiation effect between the two rays is still unclear. Based on TCAD, the synergistic radiation effects of ionizing/displacement damage caused by mixed neutrons and gamma rays are simulated. The results demonstrate that the synergistic effects are more serious than the simple sum of the two radiation effects due to their mutual enhancement. The change of the carrier recombination rate in the device at different positions shows that the displacement effects increase the peak value of surface recombination rate; meanwhile, the ionizing dose effects enhance the recombination process in bulk silicon. The mechanism of this phenomenon is that positive charges from the oxide layer and interface enhance the recombination of carriers in bulk, and the reduced carrier lifetime caused by defects from bulk makes carriers more likely to be trapped by the interface traps. In addition, the simulation result which shows the influence of temperature on the synergistic effects indicates that the synergistic effects are more sensitive to the lower temperature.

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.

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.

Enhanced Active Filter for Single-Phase Controlled Rectifier Applications

Active filter can be used to increase the performance of single-phase controlled rectifier by reducing the generated ripple and harmonic distortion. Active filter can also increase power factor and efficiency of thyristor. In this work, active filter was designed by using NPN Bipolar Junction Transistor (BJT) compared with active filter created by utilizing NPN Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The obtained efficiency of BJT based active filter with firing angles of 0° to 90° were 87.01% - 96.67%. Whereas, MOSFET based active filter produced comparable efficiency between 90.62% - 96.07%. It can be seen that MOSFET based active filter produced higher efficiency at firing angle of 0° which was 90.62% compared to BJT based active filter that has produced efficiency of 87.01% at the same firing angle. Both active filters obtained similar power factors within the range of 0.57 lagging – 0.92 lagging. It is expected that this work can be useful for the design of active filters for various power electronics applications including the design of High Voltage Direct Current (HVDC) power transmission system.

Evaluation of operation lifetime of microwave low noise NPN bipolar junction transistor

In this paper, the lifetime of microwave low noise NPN bipolar junction transistor under three operation modes are deeply investigated. Experiment results shows that the electrical parameters keep nearly unchanged when a steady electrical stress is applied over 2000 h at 125°C. The junction temperature (Tj) is found to have a significant influence on the operation lifetime. The samples begin to fail once Tj is higher than 225°C. Furthermore, the higher the junction temperature is, the earlier the failure occurs, and the shorter the lifetime is. The accumulated damages near Si/SiO2 interface around BE junction are contributed to the failure under high temperature. The estimated mean time to failure based on the failure data under high Tj is higher than that from non-failure data under low Tj. HTRB stress are found to be able to result in damages around LOCOS edge under BC junction, but the induced variation of related electrical parameters is still far below the specified failure criterion. All these data obtained here can provide a reliability foundation for bipolar transistors.

Temperature Dependent Reliability of Polysilicon Emitter Bipolar Transistors Under High Current Stress

Temperature dependent high forward current stress induced drift of electrical parameters (current gain ( ${\beta }$ ) variations, emitter resistance ( R $_{E}$ ) decrease) in polysilicon emitter bipolar transistors has been revealed. It shows that the ambient temperature surrounding the test device, i.e., the lattice temperature, plays a key role in the reliability issues of the polysilicon emitter bipolar junction transistors under high forward current stress. However, both results from technology computer-aided design (TCAD) simulation and experimental test indicate that the junction temperature only rise up to a certain extent but not very high, i.e., the widely reported self-heating effect is not the essential reason for the device damage in the case of double-polysilicon self-aligned NPN bipolar junction transistor.

Ultra High-efficiency Integrated Mid Infrared to Visible Up-conversion System

In this paper, we have introduced and investigated an integrated optoelectronic chip for the up-conversion of mid-infrared to visible light. A thin layer of the nanocrystalline photoconductive PbSe is put on the Base of the NPN bipolar junction transistor and a doped phosphorescence organic light-emitting diode is placed on the Collector contacts. The incoming mid-infrared light is converted into an electric current by quantum dot photodetector, then amplified by the NPN bipolar junction transistor, and finally, the amplified current is driven through the Collector in the organic light-emitting diode. The organic light-emitting diode is designed to emit a green color. Our findings indicated that the proposed devices provide an up-conversion process from mid-infrared to visible light with a high-efficiency rate. The quantum dot photodetector is designed to detect 3 μm and also the organic light-emitting diode works at 523 nm. It is easy to tune the 3 ~ 5 μm incoming light by tuning the PbSe quantum dots, and the output light is tuned by tuning the organic light-emitting diode structure. Thus, the proposed structure is highly flexible regarding receiving mid-infrared and generating visible light. It is concluded that the external quantum efficiency for the proposed structure for 3 μm to 523 nm is 600. Also, the enhancement of the transistor current gain (β) can further increase the conversion efficiency of the proposed device. Moreover, different structures such as Darlington can be used instead of the bipolar junction transistor to enhance conversion efficiency.

Dependence of decay time of the photocurrent induced by transient ionizing radiation on TID in NPN bipolar transistors

When an NPN bipolar junction transistor (BJT) is exposed to the pulsed gamma (or X) irradiation, photocurrent is generated, containing the primary photocurrent and the secondary photocurrent. TID experiments and transient irradiation experiments were carried out. The results show that, as accumulating total ionizing dose (TID), the secondary photocurrent decays more severely, whereas the primary photocurrent is almost impervious. Moreover, the influence of TID on the secondary photocurrent decay is related to the BJT’s collector current. If the BJT is working under the condition of high injection, the influence of TID is quite weak, but it’s evident when the BJT is working under the medium or low injection condition. The charge control model is used to analyze the decay time of the secondary photocurrent. As a result, the base minority lifetime determines the decay time, and a method how to obtain the equivalent lifetime after TID accumulation is proposed to predict the change of the decay time. Consequently, the deductive results give good agreement with the experimental results.

Effect of electric field on radiation defects in NPN transistors

In this paper, the effect of electric field on the radiation defects in gate controlled NPN (GNPN) bipolar junction transistors is firstly investigated by heavy ion irradiation and first principle calculation. Defects induced by 40 MeV silicon (Si) ions under different gate voltage of −10 V, 0 V, 10 V are measured by deep level transient spectroscopy (DLTS). Based on DLTS analyses, it is shown that 40 MeV Si ions can produce four kinds of displacement defects, and the displacement defects are affected by various gate voltages. Under positive bias and zero bias, lower migration barrier and longer migration path leads to higher concentration of V-O. Under negative bias, higher migration barrier and shorter migration path leads to combination between monovacancies, forming V2. According to first principle calculation, both hydrogen form bridge between two silicon atoms at the surface and electrons cannot significantly introduce interface traps, which is the similar under the positive and negative gate bias. The hydrogen in silicon attracted by negative bias can migrate to surface forming more interface traps and hydrogen.

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.

Improvement in electrical characteristics of Silicon on Insulator (SOI) transistor using graphene material

This paper presents the electrical characteristics of a short channel Silicon on Insulator (SOI) transistor with a graphene layer. The graphene sheet is used at the bottom of the channel close to the source side and a proportionally heavily p-type retrograde doping implanted in nearly middle of the channel. To increase the gate electrostatic control over the channel we incorporated a high-K material i.e. HfO2 as the gate oxide insulator. Due to Graphene growth and Retrograde Doping in the Channel, we called this structure “GRDC-SOI” transistor. Because graphene sheet has low band gap and high mobility, we used it to increase the on-state current. Engineered p-type retrograde doping utilized for both decreasing off-state current and increasing on-state current. These dopants cause impurity scattering in the depth of the channel and deflect electron movements and decrease off-current. On the other hand, these dopants which are located almost in the middle of the channel can play the role of base in an NPN Bipolar Junction Transistor (BJT), and turn it on and exceed the on-state current. An immense comparison among our proposed device and a device similar to GRDC-SOI but without Graphene sheet (RDC-SOI) and a conventional structure shows that our proposed device has superior electrical characteristics in terms of ION/IOFF ratio, transconductance, subthreshold slope, leakage current, breakdown voltage and short channel effects like hot carriers injection and DIBL. Our analyses demonstrate that GRDC-SOI transistor can open a window for utilizing Graphene material in digital circuits and system on chip applications.