Influence of the Metal–Semiconductor Interface Model on Power Conservation Principle in a Simulation of Bipolar Devices

The purpose of the study is to present a proper approach that ensures the energy conservation principle during electrothermal simulations of bipolar devices. The simulations are done using Sentaurus TCAD software from Synopsys. We focus on the drift-diffusion model that is still widely used for power device simulations. We show that without a properly designed contact(metal)–semiconductor interface, the energy conservation is not obeyed when bipolar devices are considered. This should not be accepted for power semiconductor structures, where thermal design issues are the most important. The correct model of the interface is achieved by proper doping and mesh of the contact-semiconductor region or by applying a dedicated model. The discussion is illustrated by simulation results obtained for the GaN p–n structure; additionally, Si and SiC structures are also presented. The results are also supported by a theoretical analysis of interface physics.

Investigation of turn-on performance in 1.2-kV MOS-bipolar devices

In this paper, the turn-on characteristics of 1.2-kV Trench IGBT (TIGBT) and Trench Clustered IGBT (TCIGBT) are investigated through TCAD simulations and experiments. TCIGBT shows much lower turn-on energy loss (Eon) due to higher current gain than an equivalent TIGBT and the negative gate capacitance effect is effectively suppressed in the TCIGBT by its self-clamping feature and PMOS action. In addition, the impact of 3-D scaling rules on the turn-on performance of TIGBT and TCIGBT is analyzed in detail. Simulation results show that scaling rules result in a significant reduction of Eon in both TIGBT and TCIGBT. Furthermore, the experimental results indicate that TCIGBT technology is well suited for high current density operations with low power losses. Compared to the state-of-the-art IGBT technology, an 18 % reduction of total power losses can be achieved by the TCIGBT operated at 300 A/cm2 and 175 °C.

Randomized comparative study of the effectiveness and safety of various bipolar devices during electrosurgical vaginal hysterectomy

AIM: The aim of this study was to investigate the morphometric features of tissues after exposure to bipolar energy of various electrosurgical generators and surgical hemostatic instruments used in vaginal hysterectomy. MATERIALS AND METHODS: The study included 48 individuals who underwent a vaginal hysterectomy. The patients were divided in three groups based on the instrument used for sealing blood vessels: a BiClamp was applied in Group 1 (n = 16), a TissueSeal PLUS COMFORT in Group 2 (n = 16), and a Thunderbeat in Group 3 (n = 16). The maximum temperature of tissue measured using a Fluke FLK TIS 40 9HZ thermal imaging infrared camera was compared within the groups. RESULTS: The maximum tissue temperature between the branches on electroligation, the minimum tissue temperature, and the tissue temperature at the coagulation boundary were significantly lower when using a TissueSeal PLUS COMFORT clamp than when using BiClamp and Thunderbeat clamps (H value = 41.8, p 0.01). Morphometric parameters (prevalence, coagulation depth and area) were the smallest with a TissueSeal PLUS COMFORT clamp compared to other clamps. CONCLUSIONS: Using a TissueSeal PLUS COMFORT clamp during vaginal hysterectomy is effective and safe and has the best thermometric and morphometric characteristics when applied to the tissue, thereby reducing the risk of lateral thermal damage. The possibility of perifocal heat transfer varies with the type of tool and with the temperature at the coagulation boundary.

Thermal Conductance Through the Skull Base From Endoscopic Surgery Cauterization Instruments: Cadaver and Goat Model

Objective Cauterization prevents hemorrhage and optimizes the surgical field during endoscopic sinus surgery but may cause injury to nearby structures. The objective of this study is to examine thermal conductance from cauterization equipment across the skull base. Study Design Cadaver and animal model. Setting Surgical skills laboratory of an academic tertiary medical institution. Methods A pilot study was conducted with a deidentified cadaver head and expanded to a goat head animal model. Endoscopic dissection was performed to expose the lamina papyracea, ethmoid roof, sphenoid roof, and frontal sinus. Cautery was applied to the frontal sinus of goat heads, and temperatures were measured via thermocouple sensors placed along the intracranial skull base. Surgical instruments studied included monopolar, bipolar, and endoscopic bipolar devices at various power settings. Results Temperature increase, as averaged across all cautery powers and measurement positions, was highest for the monopolar cautery (17.55 °C) when compared with the bipolar and endoscopic bipolar devices (<2 °C for bipolar, Endo-Pen, Stammberger, and Wormald; P < .001). Monopolar cautery reached 30.86 °C at high power when averaged over all positions ( P < .001) as compared with <3 °C for the other instruments. Temperatures rose as power of cautery was increased from low to medium and high. Temperatures decreased as the distance of the thermocouple sensor probe from the cautery origin increased. Conclusion Thermal conductance across the skull base varies depending on equipment and power of cautery, with monopolar resulting in the largest temperature increase. Choice and implementation of cauterization instruments have implications on inadvertent transmission of thermal energy during endoscopic sinus surgery.

Impact of Work function Engineering in Charge Plasma Based Bipolar Devices

In this paper, we have explored and justified the reason behind the degradation in the cutoff frequency of the bipolar transistors evolved from the charge plasma concept. It has been observed that if the work function difference present between the emitter metal contact and silicon is greater than or equal to 0.68 eV ( ϕ m - ϕ SI = 4.05 eV - 4.73 eV), it results in increment in the base width which is the inverse of the cutoff frequency. On top of this, two dimensional TCAD simulation of the different bipolar devices also demonstrate the same base width widening effect into the intrinsic region which is present between the base region and collector region. Apart from this, if this difference is exactly equal to 0.5 eV ( ϕ m - ϕ SI = 4.23 eV - 4.73 eV) then the base width widening effect can be completely eliminated from the bipolar devices base on the charge plasma.