NPN Bipolar Transistors Research Articles

Separation of Ionization Traps in NPN Transistors Irradiated by Lower Energy Electrons

Effects of oxide-trapped charge and interface traps induced by ionizing radiation, on the degradation of the electrical properties in NPN bipolar junction transistors (BJTs), are identified in this paper. Ionization traps in 3DG110 NPN BJTs are caused by 110 keV electron irradiations for various fluences, and the key electrical parameters are measured in situ during irradiation. In order to separate the effects of the interface traps and oxide charge on the radiation response in BJTs, the isochronal and isothermal annealing are performed after irradiations. Behavior of the radiation-induced defects is detected by DLTS after the irradiation and the postirradiation annealing. Measurement results indicate that when the change in reciprocal of the gain (Δ(1/ β)) tends to level off, the concentration of oxide-trapped charge increases with increasing irradiation fluence, while that of the interface traps keeps unchangeable. A comparison of DLTS signals with changes in excess base current (ΔI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> ) versus base-emitter voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BE</sub> ) is conducted to show the role of oxide-trapped charge and interface traps on the excess base current, illustrating that the DLTS analysis is suitable to separate the ionization traps in BJTs.

Annealing effects and DLTS study on NPN silicon bipolar junction transistors irradiated by heavy ions

Isochronal anneal sequences have been carried out on 3DG112 silicon NPN bipolar junction transistors (BJTs) irradiated with 20MeV bromine (Br) heavy ions. The Gummel curve is utilized to characterize the annealing behavior of defects in both the emitter-base depletion region and the neutral base. We find that the base current (IB) decreases with the increasing annealing temperature, while the collector current (IC) remains invariable. The current gain varies slightly, when the annealing temperature (TA) is lower than 400K, while varies rapidly at TA<450K, and the current gain of the 3DG112 BJT annealing at 700K almost restore to that of the pre-radiation transistor. Deep level transient spectroscopy (DLTS) data is used to assign the relative magnitude of each of the important defects. Based on the in situ electrical measurement and DLTS spectra, it is clear that the V2(−/0)+V-P traps are the main contribution to the degradation of current gain after the 20MeV Br ions irradiation. The V2(−/0)+V-P peak has many of the characteristics expected for the current gain degradation.

A Linearization Technique for a Transconductor Using Vertical Bipolar Junction Transistors in a CMOS Process

In this paper, a linearization technique for a transconductor using vertical NPN (V-NPN) bipolar junction transistors (BJTs) in a deep n-well CMOS process is proposed to achieve high linearity performance without degrading power efficiency and noise performance. The proposed transconductor consists of a V-NPN BJT pseudodifferential transconductor (PDT) and a V-NPN BJT fully differential transconductor (FDT). The linearity of the proposed transconductor is improved by canceling the negative peak value of gm'' in the FDT with the positive one in the PDT and by making overall gm'' of the proposed transconductor close to zero. To verify the proposed linearization method, an RF amplifier and a first-order Gm-C low-pass filter adopting the proposed transconductor are designed and implemented in a 0.18-μm deep n-well CMOS process. The implemented RF amplifier and Gm-C low-pass filter achieve 5.8- and 8.5-dB improvements over conventional circuits in the output-referred third-order intercept point, respectively.

Incident particle range dependence of radiation damage in a power bipolar junction transistor

The characteristic degradations in silicon NPN bipolar junction transistors (BJTs) of type 3DD155 are examined under the irradiations of 25-MeV carbon (C), 40-MeV silicon (Si), and 40-MeV chlorine (Cl) ions respectively. Different electrical parameters are measured in-situ during the exposure of heavy ions. The experimental data shows that the changes in the reciprocal of the gain variation (Δ(1/β)) of 3DD155 transistors irradiated respectively by 25-MeV C, 40-MeV Si, and 40-MeV Cl ions each present a nonlinear behaviour at a low fluence and a linear response at a high fluence. The Δ(1/β) of 3DD155 BJT irradiated by 25-MeV C ions is greatest at a given fluence, a little smaller when the device is irradiated by 40-MeV Si ions, and smallest in the case of the 40-MeV Cl ions irradiation. The measured and calculated results clearly show that the range of heavy ions in the base region of BJT affects the level of radiation damage.

Effect of bias condition on heavy ion radiation in bipolar junction transistors

The characteristic degradations in a silicon NPN bipolar junction transistor (BJT) of 3DG142 type are examined under irradiation with 40-MeV chlorine (Cl) ions under forward, grounded, and reverse bias conditions, respectively. Different electrical parameters are in-situ measured during the exposure under each bias condition. From the experimental data, a larger variation of base current (IB) is observed after irradiation at a given value of base-emitter voltage (VBE), while the collector current is slightly affected by irradiation at a given VBE. The gain degradation is affected mostly by the behaviour of the base current. From the experimental data, the variation of current gain in the case of forward bias is much smaller than that in the other conditions. Moreover, for 3DG142 BJT, the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence, while at high fluence, the gain degradation in the reverse bias case becomes smaller than that in the grounded case.

Some features of degradation in bipolar transistors at different test conditions for total ionizing dose effect

The results of studying the degradation in PNP and NPN bipolar transistors at different test conditions for total ionizing dose effect are presented. It is confirmed that the gain change at total ionizing dose testing depends strongly on the electrical conditions. The features of the dose rate impact at the degradation of transistors in a wide range of doses are described.

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.

DLTS Studies of bias dependence of defects in silicon NPN bipolar junction transistor irradiated by heavy ions

The characteristic degradation in silicon NPN bipolar junction transistors (BJTs) of 3DG130 type is examined under the irradiation with 35MeV silicon (Si) ions under forward, grounded and reverse bias conditions, respectively. Different electrical parameters were in-situ measured during the exposure under each bias condition. Using deep level transient spectroscopy (DLTS), deep level defects in the base-collector junction of 3DG130 transistors under various bias conditions are measured after irradiation. The activation energy, capture cross section and concentration of observed deep level defects are measured using DLTS technique. Based on the in situ electrical measurement and DLTS spectra, it is clearly that the bias conditions could affect the concentration of deep level defects, and the displacement damage induced by heavy ions.

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.

Low Noise and Highly Linear Wideband CMOS RF Front-End for DVB-H Direct-Conversion Receiver

In this paper, a wideband CMOS radio frequency (RF) front-end for digital video broadcasting-handheld (DVB-H) receiver is proposed. The RF front-end circuit is composed of a single-ended resistive feedback low noise amplifier (LNA), a single-to-differential amplifier, an I/Q down-conversion mixer with linearized transconductors employing third order intermodulation distortion cancellation, and a divide-by-two circuit with LO buffers. By employing a third order intermodulation (IMD3) cancellation technique and vertical NPN bipolar junction transistor (BJT) switching pair for an I/Q down-conversion mixer, the proposed RF front-end circuit has high linearity and low low-frequency noise performance. It is fabricated in a 0.18µm deep n-well CMOS technology and draws 12mA from a 1.8V supply voltage. It shows a voltage gain of 31dB, a noise figure (NF) lower than 2.6dB, and an IIP3 of -8dBm from 470MHz to 862MHz.

NPN bipolar effect and its influence on charge sharing in a tripe well CMOS technology with n+ deep well

In this paper, we investigate the charge sharing collection induced by heavy ion radiation in a tripe well CMOS technology with n+ deep well though 3-D TCAD device simulation. Result shows that n+ deep well will induce the parasitical NPN bipolar transistor, and therefore enhance the charge sharing between NMOS remarkably. The enhancement factor is 24 times that in PNP bipolar in dual well technology. Furthermore, the effects of n-well contact and p-well contact on NPN bipolar are studied. The result shows that the NPN bipolar enhancement factor will decrease with the increase of p-well contact area and with the decreasing of its distance to device, while the NPN bipolar enhancement factor will increase with the increase of n-well contact area.

60Co γ-ray induced gain degradation in bipolar junction transistors

Commercial indigenously made npn and pnp bipolar junction switching transistors used for space applications are investigated for 60Co γ-ray induced effects. The on-line as well as off-line measurements indicate that the forward current gain of the transistors decreases significantly as the accumulated dose increases. Excess base current model is employed to account for the current gain degradation. The pnp transistor undergoes as much degradation as the npn type. It is found that bulk degradation by displacement damage is the dominant mechanism leading to reduction in forward current gain of npn transistors. On the other hand it appears that, in addition to bulk damage, surface degradation due to accumulation of interface states at the silicon-silicon dioxide interface also contributes significantly to gain degradation in pnp transistor as evident from thermal annealing studies. Further, estimation reveals that the transistor with larger base width has higher displacement damage factor.

Effects of orientation of substrate on the enhanced low-dose-rate sensitivity (ELDRS) in NPN transistors

The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with 〈111〉 orientation was more sensitive to ionizing radiation than that with 〈100〉 orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.

Effect of 3.0 MeV helium implantation on electrical characteristics of 4H-SiC BJTs

Degradation of 4H-SiC power bipolar junction transistors (BJTs) under the influence of a high-energy helium ion beam was studied. Epitaxially grown npn BJTs were implanted with 3.0 MeV helium in the fluence range of 1010–1011 cm−2. The devices were characterized by their current–voltage (I–V) behaviour before and after the implantation, and the results showed a clear degradation of the output characteristics of the devices. Annealing these implanted devices increased the interface traps between passivation oxide and the semiconductor, resulting in an increase of base current in the low-voltage operation range.

Radiation effects on bipolar junction transistors induced by 25 MeV carbon ions

The characteristic degradation in silicon NPN bipolar junction transistors (BJTs) of 3DG112 type is examined under the irradiation with 25MeV carbon (C) ions and various bias conditions. Different electrical parameters were measured in-situ during the exposure under each bias condition. From the experimental data, larger variation of base current (IB) is observed after irradiation at a given value of base-emitter voltage (VBE), while the collector current is only slightly affected by irradiation at a given VBE. The gain degradation is mostly affected by the behavior of the base current. The change in the reciprocal of current gain (Δ(1/β)) increases linearly with increasing the C ions fluence. The degradation of the NPN BJTs under various bias conditions during irradiation was studied. Compared to the case where the terminals are grounded, at a given fluence, the change in the reciprocal of current gain varies slightly less when the base-emitter junction is forward biased. On the other hand, there is no distinction for the change in the reciprocal of current gain between the case of reverse-biased base-emitter junction and that of all terminals grounded for the NPN BJTs at a given fluence.

Design, Manufacture and Performance of Germanium Bipolar Transistors

Germanium NPN bipolar transistors have been manufactured using phosphorus and boron ion implantation processes. Implantation and subsequent activation processes have been investigated for both dopants. Full activation of phosphorus implants has been achieved with RTA schedules at 535C without significant junction diffusion. However, boron implant activation was limited and diffusion from a polysilicon source was not practical for base contact formation. Transistors with good output characteristics were achieved with an Early voltage of 55V and common emitter current gain of 30. Both Silvaco process and device simulation tools have been successfully adapted to model the Ge BJT(bipolar junction transistor) performance.

Degradation mechanisms of current gain in NPN transistors

An investigation of ionization and displacement damage in silicon NPN bipolar junction transistors (BJTs) is presented. The transistors were irradiated separately with 90-keV electrons, 3-MeV protons and 40-MeV Br ions. Key parameters were measured in-situ and the change in current gain of the NPN BJTS was obtained at a fixed collector current (Ic = 1 mA). To characterise the radiation damage of NPN BJTs, the ionizing dose Di and displacement dose Dd as functions of chip depth in the NPN BJTs were calculated using the SRIM and Geant4 code for protons, electrons and Br ions, respectively. Based on the discussion of the radiation damage equation for current gain, it is clear that the current gain degradation of the NPN BJTs is sensitive to both ionization and displacement damage. The degradation mechanism of the current gain is related to the ratio of Dd/(Dd + Di) in the sensitive region given by charged particles. The irradiation particles leading to lower Dd/(Dd + Di) within the same chip depth at a given total dose would mainly produce ionization damage to the NPN BJTs. On the other hand, the charged particles causing larger Dd/(Dd + Di) at a given total dose would tend to generate displacement damage to the NPN BJTs. The Messenger–Spratt equation could be used to describe the experimental data for the latter case.

Effects of Total Ionizing Dose on Bipolar Junction Transistor

Problem statement: The amount of ionizing radiation that Bipolar Junction Transistor (BJT) devices encounter during their lifecycle degrades both of their functional and electrical parameter performances. The different radiation environments either in space, high energy physics experiments, nuclear environment or fabrication process as well as for standard terrestrial operation possess an impact on the devices. Approach: In this research, analytical studies of the effects of ionizing radiation introduced in Commercial-Off-The Shelf (COTS) NPN BJTs by 60Co gamma (I³) rays had been performed. Results: It was observed that exposure of BJTs to 60Co caused ionizing radiation damage. Ionizing radiation damage was caused mainly by excess charges trapped on or near the surfaces of their insulating layers and interfaces. This phenomenon reduced the minority carrier lifetime and thus, leading to a decrease in the current gain of the BJTs. Conclusion: This ionizing radiation effect was found to arouse either a permanent or temporarily damage in the devices depending on their current drives and also the Total Ionizing Dose (TID) absorbed. The performance and degradation of selected BJT devices during irradiation with respect to total dose 60Co were presented in this study. © 2010 Science Publications.

Ionization damage in NPN transistors caused by lower energy electrons

Electrical degradation of two type NPN bipolar junction transistors (BJTs) with different emitter sizes was examined under exposures of 70 and 110keV electrons. Base and collector currents as a function of base–emitter voltage were in-situ measured during exposure. Experimental results show that both the 70 and 110keV electrons produce an evident ionization damage to the NPN BJTs. With increasing fluence, collector currents of the NPN BJTs hardly change in the whole range of base–emitter voltage from 0 to 1.2V, while base currents increase in a gradually mitigative trend. Base currents vary more at lower base–emitter voltages than at higher ones for a given fluence. The change in the reciprocal of current gain at a fixed base–emitter voltage of 0.65V increases non-linearly at lower fluences and tends to be gradually saturated at higher fluences. Sensitivity to ionization damage increases for BJTs with an emitter having a larger perimeter-to-area ratio.

Fast Switch-Off of High Voltage 4H–SiC npn BJTs from Deep Saturation Mode

In this paper, very fast switch-off of high voltage 4H–SiC npn Bipolar Junction Transistors (BJTs) driven in deep saturation regime is reported. It is shown that the switch-off time can be as short as 4 ns if a reverse base current pulse is applied that provides forced minority carrier sweep out from the base.