Papers by Keyword: Bipolar Transistor

Abstract: In this study, we introduce the impact of gamma irradiation on 4H-SiC based transistor-transistor logic (TTL) inverters. These monolithic bipolar inverters have been successfully demonstrated in a broad spectrum of temperature and supply voltage conditions. In this iteration of experiments, attempts made to the processing to increase beta values. The gamma radiation tests from a ⁶⁰Co source were conducted under various operation conditions and measured in-situ under different biasing conditions. The Silicon Carbide Integrated circuits ( SiC ICs) show excellent tolerance properties to gamma radiation up to doses of nearly 1 MRad. Comparable Si BJT-based TTL inverters show considerable degradation already at one order of magnitude lower doses, clearly demonstrating the superior radiation hardness of 4H-SiC ICs.

Abstract: In this paper the Bipolar Mode Field Effect Transistor (BMFET) is demonstrated for the first time in 4H-SiC. The structure is based by two p⁺-type regions symmetrically placed at both sides of a n-type region channel and the device implements two control mechanisms: into the channel the potential barrier controls the electron flow in the off-state operations, like VJFET-based devices, whereas, during the on-state, the holes injected from the p-n junctions induce the conductivity modulation of the channel reducing the on-resistance with beneficial effects on current gain and switching operations. In order to avoid the reduction of carrier lifetime into the channel due to ion implantation and trench etching, an ad-hoc fabrication process has been set-up to enable the conductivity modulation into the channel. First experimental tests on the prototypes show the correct operations of the device as demonstrated from the changing of the output characteristic from triode-like to pentode-like behaviors, which are ascribed to the two main operation principles of the device.

Abstract: In order to find the influence of ESD initial injected voltage on sensitive port of some high-frequency low-noise silicon bipolar transistors, some electrostatic discharge (ESD) experiments were taken on 9014 and 2SA812, which are beneficial to study the relevant law of ESDS (ESD sensitivity). The results show that the reverse-biased collector-base junction of 9014 and 2SA812 satisfied the law of latent damage. Besides, the ESD initial injected voltage is inversely proportional to the number of ESD before the device out of work, and proportional to the failure voltage.

Abstract: In order to find the most sensitive port of some high-frequency low-noise silicon bipolar transistors, some electrostatic discharge (ESD) experiments were taken on three typical devices, which is beneficial to study the relevant law of ESDS (ESD sensitivity). Based on the experimental results, reverse-biased emitter-base junction was compared with reverse-biased collector-base junction about failure voltage under the action of HBM ESD, MM ESD and BMM ESD. The results show that the sensitive port is different for those mentioned silicon bipolar transistors under the action of different ESD models. Consequently, the most sensitive port of high-frequency low-noise silicon bipolar transistors may be variable for different ESD models.

Abstract: SiC BJTs are very attractive for high power application, but long term stability is still problematic and it could prohibit commercial production of these devices. The aim of this paper is to investigate the current gain degradation in BJTs with no significant degradation of the on-resistance. Electrical measurements and simulations have been used to characterize the behavior of the BJT during the stress test. Current gain degradation occurs, the gain drops from 58 before stress to 43 after 40 hours, and, moreover, the knee current shows fluctuations in its value during the first 20 hours. Current gain degradation has been attributed to increased interface traps or reduced lifetime in the base-emitter region or small stacking faults in the base-emitter region, while fluctuations of the knee current might be due to stacking faults in the collector region.

Abstract: Vertical epitaxial NPN SiC BJTs for 1200 V rating were fabricated. Very low collector-emitter saturation voltages VCESAT=0.5 V at IC=6 A (JC=140 A/cm2) and T=25 °C and VCESAT=1.0 V at IC=6 A and T=250 °C were measured. The common emitter current gain at IC=6 A is 71 at T=25 °C and 32 at T=250 °C, respectively. A SPICE model was developed for the BJT including the parasitic capacitances of the internal pn junctions, as well as temperature dependence of the current gain and the collector series resistance. The IC-VCE characteristics of the BJT are in good agreement with the SPICE model between 25 °C and 250 °C. Fast switching measurements were performed showing a VCE voltage fall-time of 22 ns and a VCE voltage rise-time of 11 ns.

Abstract: Homoepitaxial growth has been performed on Si-face nominally on-axis 4H-SiC substrates. Special attention was paid to the surface preparation before starting the growth. Si-face polished surfaces were studied after etching under C-rich, Si-rich and under pure hydrogen ambient conditions. In-situ surface preparation, starting growth parameters and growth temperature are found to play a vital role to maintain the polytype stability in the epilayer. High quality epilayers with 100% 4H-SiC were obtained on full 2” wafer. Complete PiN structure was grown and more than 70% of the diodes showed a stable behavior and the forward voltage drift was less than 0.1 V. Also, a comparison of the electroluminescence images of diodes before and after heavy injection of 125 A/cm2 for 30 min did not show any sign of stacking fault formation in the device active region.

Abstract: Microelectronics is a central area within information technology, which is still one of the most important global technologies. It will be shown that the development of integrated circuits is based on a long and fascinating history, which is unique in modern time. Yet, the fantastic growth in semiconductor electronics is due to a unique combination of basic conceptional advances, the perfection of new materials and the development of new device principles. A brief survey of the development of microelectronics is given by not only focusing on the history of microelectronics but also taking into account materials and market aspects. Since microelectronics is an extremely complex area, a few criteria and reference points for integrated circuits are given. Thereafter, some examples are presented indicating the rapidly changing state-of-the-art. It will be shown that the development of material science within the area of microelectronics is not always driven by scientific curiosity but often by arbitrary and not always obvious preferences. After a short discussion of the performance advantages and disadvantages of germanium, silicon and III-V compound semiconductors, the SiGe heterojunction bipolar transistor is taken as an example for demonstrating a few important differences in the performance of all-silicon devices with regard to silicon-based heterojunction devices in general. In conclusion, the impact of human enterprise and research policy on the development of microelectronics is briefly discussed.