Gain Of Bipolar Transistors Research Articles

The Analysis of SCR-Based ESD Protection Circuit with P-Drift and N+ Floating Region

In this paper, a novel SCR (Silicon Controlled Rectifier)-based ESD(Electrostatic Discharge) protection circuit for power clamp is proposed. The proposed protection circuit has high holding voltage due to floating n+ region which reduces current gain of parasitic bipolar transistor. This characteristic makes it ensure latch-up immunity. The electrical characteristics of the proposed ESD protection circuit have been simulated by using Synopsys TCAD simulation tool. According to the simulation results, the proposed protection circuit has high holding voltage of about 4.61V to 8.75V as design variation. Also, it is verified by using TLP (Transmission Line Pulse) system. As a result of measurement, it has holding voltage of 15.7V to 19.35V as design variation and high robustness above HBM 6kV, MM 600V.

Synergistic Effect of Ionization and Displacement Damage in NPN Transistors Caused by Protons With Various Energies

Based on 2N2222 NPN bipolar junction transistors (BJTs), synergistic effect between ionization and displacement defects induced by 3 MeV, 5 MeV and 10 MeV protons were researched. High-energy protons can be incident upon the silicon (Si) BJTs, producing displacement defects in silicon bulk and ionization damage in the oxide layer of BJTs, respectively. Both ionization and displacement damage result in the degradation of current gain of BJTs. At a given displacement dose, 10 MeV protons induce the maximum degradation of current gain of 2N2222 NPN BJTs, while 3 MeV protons cause the minimum degradation. In this case, non-ionizing energy loss (NIEL) methodology is not suitable to normalize the displacement damage induced by 3 MeV, 5 MeV and 10 MeV protons, which is attributed to the synergistic effect of ionization and displacement damage. The displacement defect centers in based-collector junction of 2N2222 transistor induced by 3 MeV, 5 MeV and 10 MeV proton exposures, were discovered and characterized by deep level transient spectroscopy (DLTS). Based on the comparison between the electrical parameters and the DLTS results, it is shown that, interface traps due to ionization damage induced by high-energy protons spread the emitter-base depletion layer, leading to the enhancement effects to displacement damage in the base-collector junction of NPN BJT. Meanwhile, bias voltage used during DLTS measurement influence characteristics of DLTS signals. With the increasing reverse bias, the value of $\Delta {\rm C}/{\rm C}$ for VO, ${{\rm V}_2}(= / -)$ , E4 and ${\rm V}_{2}(- /0) + {\rm E}5$ centers increases.

Temperature dependence of current gain in 4H-SiC bipolar junction transistors

The temperature dependence of current gain from 140 to 460 K in 4H-SiC bipolar junction transistors (SiC BJTs) was investigated. The current gain increased from 110 to 1200 with decreasing temperature from 460 to 200 K. The high current gain at the low temperature can be ascribed to the enhanced incomplete ionization of aluminum acceptors in the base layer, resulting in the increase in injection efficiency. However, when the temperature was further reduced from 200 to 140 K, the current gain decreased from 1200 to 515, which is caused by high injection condition in the base layer, because of a very low hole concentration below 200 K.

Bias dependence of synergistic radiation effects induced by electrons and protons on silicon bipolar junction transistors

Abstract Bias dependence on synergistic radiation effects caused by 110 keV electrons and 170 keV protons on the current gain of 3DG130 NPN bipolar junction transistors (BJTs) is studied in this paper. Experimental results indicate that the influence induced by 170 keV protons is always enhancement effect during the sequential irradiation. However, the influence induced by 110 keV electrons on the BJT under various bias cases is different during the sequential irradiation. The transition fluence of 110 keV electrons is dependent on the bias case on the emitter–base junction of BJT.

Influence of Passivation Oxide Thickness and Device Layout on the Current Gain of SiC BJTs

The effect of passivation oxide thickness and layout on the current gain of SiC bipolar junction transistors is reported. Different thicknesses of plasma enhanced chemical vapor deposited (PECVD) silicon dioxide in the range 50-150 nm were deposited prior to the same annealing process in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O, and their effect on the transistor gain was investigated for different device layouts. For a fixed device layout, ~60 % higher gains were observed for oxide thicknesses ranging between 100 and 150 nm with current gains of ~200 at room temperature and >100 at 300 °C. For each tested thickness of deposited oxide, device layout providing lower collector resistance achieved slightly higher gains.

An alternative method for using bipolar junction transistors as a radiation dosimetry detector in breast cancer treatment

Silicon photodetectors and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are frequently used devices for measuring ionizing radiation in health physics instrumentation. The Bipolar Junction Transistor (BJT) is not a typical device used as a detector for measuring some physical quantities in radiotherapy beams due to its loss of sensitivity to ionizing radiation, as a consequence of radiation damage in the silicon semiconductor substrate. Actually, the know-how of the BJT characteristic curves and its response to ionizing radiation leads us to suggest an alternative method to estimate the radiation dose value in breast cancer treatments. The BJT parameter to be evaluated before and after the irradiation procedure is the BJT amplification factor, also called DC gain β. In this work, the study was done using a BJT known as Darlington type, within an Alderson Rando anthropomorphic phantom. Darlington transistors have very high gain and this feature allowed that the BJT gain changes to be correlated with the dose of the radiation beam. The results indicate that this new method could be an alternative option to estimate the dose value in the phantom for measurements in breast cancer radiotherapy.

Simulation of Bipolar Transistor Degradation at Various Dose Rates and Electrical Modes for High Dose Conditions

Radiation response of bipolar devices irradiated under various electrical modes and dose rates at high doses has been studied. A nonlinear numerical model including ELDRS effects and electric field reduction at high doses has been developed and validated. Dose degradation of a bipolar transistor's gain factor at different dose rates and electrical modes has been simulated and explained in a unified way, based on dependence of the charge yield in isolation oxides on dose rates and electric fields. It has been shown that at high doses one needs to use a nonlinear, self-consistent numerical approach, accounting for simultaneous suppression of the oxide electric field induced by trapped charge. Correspondingly, two types of degradation saturation have been revealed: (i) due to simultaneous thermal annealing, and (ii) due to total dose dependent electric field reduction in oxides. The former implies proportionality of the saturation dose and degradation level to dose rate, the latter permits dose rate independent saturation levels of degradation.

Optical Measurement Techniques of Recombination Lifetime Based on the Free Carriers Absorption Effect

We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices.

Generation and recombination in two-dimensional bipolar transistors

We study the effects of recombination and generation process on the operation of bipolar junction transistor based on two-dimensional materials, and in particular, graphone. Here, we use Shockley–Read–Hall model to study these process. First, we investigate the current–voltage characteristics of a graphone p–n junction considering generation and recombination process. Then, we calculate the estimated changes in current gain, cutoff frequency, and output characteristics of a graphone bipolar junction transistor designed in a recent study.

Minimum gate trigger current degradation in 4.5 kV 4H-SiC commutated gate turn-off thyristor

The increment in minimum gate trigger current in a 4H-SiC commutated gate turn-off thyristor after the current stress test is investigated. The recombination at the intersection line of the Shockley-type stacking faults and the pn junction causes a reduction in the level of carrier injection from the anode to the gate. The current gain of the top pnp bipolar junction transistor, therefore, decreases, and the minimum gate trigger current increases. The minimum gate trigger current after the current stress test does not return to that before the current stress test at 200 °C, although the on-state voltage of the degraded thyristor returns to that of the original one when the temperature is increased to more than 150 °C. The Shockley-type stacking faults, which are parallel to the current flow from the anode to the gate and cause the increment in minimum gate trigger current, exist even if the temperature increases.

Defect Electronics in SiC and Fabrication of Ultrahigh-Voltage Bipolar Devices

Fast epitaxial growth, defect reduction, device designing, and process development in SiC toward ultrahigh-voltage (> 10 kV) bipolar devices are investigated. 100~200 um-thick 4H-SiC epilayers with a low background doping concentration in the low 10^{13} cm^{-3} can be grown at a growth rate greater than 50 um/h. Impacts of extended defects on carrier recombination are clarified in photoluminescence mapping measurements. Generation and reduction of Z_{1/2} center, the dominant lifetime killer, are summarized. After Z_{1/2} elimination by thermal oxidation at 1400^{o}C, the carrier lifetime can be enhanced to 25 us or even longer. By utilizing space-modulated junction termination extension, a 21.7 kV PiN diode is demonstrated. Through unique process development, the current gain in bipolar junction transistors is increased to 250~330.

Simultaneous and Sequential Radiation Effects on NPN Transistors Induced by Protons and Electrons

This paper examines individual radiation effects caused by 110 keV electrons and 170 keV protons, and combined radiation effects induced by 110 keV electrons together with 170 keV protons on the forward current gain of NPN bipolar junction transistors (3DG130, 3DG112). Key parameters were measured in-situ and the change in current gain of the NPN bipolar junction transistors is obtained at a fixed voltage of base-emitter junction (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BE</sub> ) during simultaneous and sequential exposures. Experimental results show that the current gain degradation of the NPN bipolar junction transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 keV electrons, while the displacement damage is mainly induced by 170 keV protons in this investigation. Based on the simultaneous and sequential exposure results, the ionization damage caused by 110 keV electrons can give an enhancing effect to displacement damage induced by 170 keV protons for NPN bipolar junction transistors.

Enhanced Current Gain (&gt;250) in 4H-SiC Bipolar Junction Transistors by a Deep-Level-Reduction Process

We demonstrate 4H-SiC bipolar junction transistors (BJTs) with an enhanced current gain over 250. High current gain was achieved by utilizing optimized device geometry as well as optimized surface passivation, continuous epitaxial growth of the emitter-base junction, combined with an intentional deep-level-reduction process based on thermal oxidation to improve the lifetime in p-SiC base. We achieved a maximum current gain (β) of 257 at room temperature and 127 at 250°C for 4H-SiC BJTs fabricated on the (0001)Si-face. The gain of 257 is twice as large as the previous record gain. We also demonstrate BJTs on the (000-1)C-face that showed the highest β of 439 among the SiC BJTs ever reported.

Synergistic Radiation Effects on PNP Transistors Caused by Protons and Electrons

This paper examines individual radiation effects caused by 110 KeV electrons, 70 KeV electrons and 170 KeV protons, and combined radiation effects induced by 110 KeV electrons together with 170 KeV protons and 70 KeV electrons with 170 KeV protons on the forward current gain of bipolar junction transistors (3CG130, PNP). The combined radiation effects include simultaneous and sequential radiation effects. Key parameters were measured in-situ and the change in current gain of the PNP transistors is obtained at a fixed voltage of emitter-base junction . Experimental results show that the current gain degradation of the PNP transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 KeV and 70 KeV electrons, while the displacement damage is mainly induced by 170 KeV protons in this investigation. Based on the simultaneous and sequential exposure results, the ionization damage caused by 110 KeV and 70 KeV electrons could give annealing-like and enhancing effects to displacement damage induced by 170 KeV protons for PNP BJTs.

Effects of base doping and carrier lifetime on differential current gain and temperature coefficient of 4H-SiC power bipolar junction transistors

4H-SiC NPN bipolar junction transistor (BJT) is studied systematically by performing two-dimensional numerical simulations. Several design issues are discussed. Depending on the doping concentration of the base and the carrier lifetimes, both positive and negative temperature coefficients in the common emitter current gain could exist in 4H-SiC NPN BJTs with aluminium-doped base. The temperature coefficients of the current gain at different base doping concentrations and different carrier lifetimes have been determined. A high base doping concentration can reduce the requirement for the carrier lifetime in order to obtain negative temperature coefficient in current gain. Device simulations are performed to evaluate the carrier lifetimes by fitting the measured output IC –VCE curves. An excellent fitting is obtained and the base electron lifetime and the emitter hole lifetime are extracted to be about 22 and 5.7 ns, respectively.

Improved Current Gain in 4H-SiC BJTs Passivated with Deposited Oxides Followed by Nitridation

We report the improvement of current gain in 4H-SiC bipolar junction transistors (BJTs) by using deposited oxides as a surface passivation layer. Various post-deposition annealing processes were investigated. We successfully demonstrated SiC BJTs with a high current gain (β) of 86 using deposited oxides annealed in NO. This is 70% higher current gain compared with that of BJTs with the same structure with conventional thermally-grown oxides.

Improvement of Current Gain in 4H-SiC BJTs by Surface Passivation With Deposited Oxides Nitrided in $\hbox{N}_{2}\hbox{O}$ or NO

We report the improvement of current gain in 4H-SiC bipolar junction transistors (BJTs) by utilizing deposited oxides as a surface passivation layer. Various post deposition annealing processes, including annealing ambient (N2, N2O, and NO) and annealing time, were investigated. We successfully demonstrate SiC BJTs with high current gains (β) of 73 and 102 using deposited oxides annealed in N2O and NO, respectively, whereas BJTs having conventional thermally grown oxides showed a current gain of 50.

Combined Radiation Effects of Protons and Electrons on NPN Transistors

This paper examines individual radiation effects caused by 110 keV electrons, 70 keV protons and 170 keV protons, and combined radiation effects induced by 110 keV electrons together with 70 keV protons and 110 keV electrons with 170 keV protons on the forward current gain of bipolar junction transistors (3DG112D, NPN). Key parameters were measured in-situ and the change in current gain of the NPN transistors is obtained at a fixed collector current. Experimental results show that the current gain degradation of the NPN transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 keV electrons, while the displacement damage is mainly induced by 170 keV protons in this study. Under the combined exposure of 170 keV protons and 110 keV electrons, the current gain degradation lies between those given by the individual irradiations. The current gain degradation is mainly caused by the 170 keV protons, and the 110 keV electrons mitigate the degradation to some extent. In the case of combined irradiation of 110 keV electrons and 70 keV protons, no synergistic effect occurs, the current gain degradation is basically controlled by the 110 keV electrons.

The Effects of Low Dose-Rate Ionizing Radiation on the Shapes of Transients in the L&gt;M124 Operational Amplifier

Shapes of single event transients (SETs) in a linear bipolar circuit (LM124) change with exposure to total ionizing dose (TID) radiation. SETs shape changes are a direct consequence of TID-induced degradation of bipolar transistor gain. A reduction in transistor gain causes a reduction in the drive current of the current sources in the circuit, and it is the lower drive current that most affects the shapes of large amplitude SETs.

A physical model of floating body effects in polysilicon thin film transistors

Based on a closed form of the base–emitter voltage of the parasitic bipolar transistor, a physical model of floating body effects is proposed for polysilicon thin film transistors, which takes into account the polysilicon graded pn junction and the generation rate including the Poole-Frenkel effect. Simulated results by this model are in good agreement with experimental data. It is shown that the action of a parasitic bipolar transistor should be taken into account only when the channel length is short enough due to the much smaller carrier mobility in polysilicon compared with single crystalline silicon. Whereas, the parasitic bipolar transistor gain (β) increases sharply with decreasing the channel length when the channel length is less than 5μm, which is due to the rapid increase of the base transport factor (αT).