Junction temperature

About: Junction temperature is a research topic. Over the lifetime, 5058 publications have been published within this topic receiving 58643 citations.

Thermal protection of traction inverters

Abstract: A method for providing thermal protection for forced air cooled power electronic semiconductors without direct measurement of semiconductor temperature, the semiconductors being mounted on a heat sink over which cooling air is blown includes the steps of computing the cooling air mass flow rate, creating an electronic model of the semiconductor/heat sink combination and estimating the semiconductor junction temperature from the mass flow rate and model. The cooling mass flow rate is determined by measuring the temperature of the cooling air prior to passage over the heat sink, measuring atmospheric pressure of the cooling air, determining the volumetric air flow rate of the cooling air and computing, from the cooling air temperature, pressure and volumetric flow rate, the cooling air mass flow rate. Power dissipation in the semiconductors is then commuted and heat sink and semiconductor temperatures are estimated from power dissipation and cooling air mass flow rate. Semiconductor power dissipation is limited so as to restrict semiconductor temperature to a safe operating value.

Revised method for extraction of the thermal resistance applied to bulk and SOI SiGe HBTs

Abstract: A revision is presented of the technique to determine the junction temperature and thermal resistance of bipolar transistors. It is based on the temperature sensitivity of the base-emitter voltage when biasing the device under constant emitter current. It accounts correctly for the self-heating of the device during the measurement. Results are obtained for devices fabricated on silicon-on-insulator (SOI) and bulk silicon having different emitter widths and lengths. An increment of the thermal resistance is found for SOI devices with respect to bulk.

High Brightness GaN Vertical Light-Emitting Diodes on Metal Alloy for General Lighting Application

Abstract: In this paper, we show the many advantages of the GaN-based vertical light-emitting diodes (VLEDs) on metal alloy over conventional LEDs in terms of: better current spreading, vertical current path for low operation voltage, better light extraction, flexible chip size scaling, higher driving current density, faster heat dissipation, and good reliability. The GaN VLED on metal alloy exhibits very good current-voltage behavior with low operated voltage and low serial dynamic resistance. The low operation junction temperature of GaN VLED on metal alloy demonstrates excellent heat dissipation capabilities. Chip size scaling without efficiency loss shows a unique property of GaN VLED on metal alloy. The GaN VLED on metal alloy also enables top surface engineering for efficient light extraction to further light output. A high-power white LED having efficiency of 120 lumen/W was achieved through a combination of reflector, surface engineering, and optimization of the n-GaN layer thickness. Coupled with good reliability and mass production ability, the GaN VLED on metal alloy is very suitable for general lighting application.

Nanoscale electro-thermal interactions in AlGaN/GaN high electron mobility transistors

Abstract: Self-heating in AlGaN/GaN high electron mobility transistors (HEMTs) negatively impacts device performance and reliability. Under nominal operating conditions, a hot-spot in the device channel develops under the drain side corner of the gate due to a concentration of volumetric heat generation leading to nonequilibrium carrier interactions and non-Fourier heat conduction. These subcontinuum effects obscure identification of the most salient processes impacting heating. In response, we examine self-heating in GaN-on-Si HEMTs via measurements of channel temperature using above-bandgap UV thermoreflectance imaging in combination with fully coupled electrothermal modeling. The methods together highlight the interplay of heat concentration and subcontinuum thermal transport showing that channel temperature cannot be determined solely by continuum scale heat transfer principles. Under conditions of equal power dissipation (PDISS = VDS × IDS = 250 mW), for example, a higher VDS bias (∼23 V) resulted in an ∼44% larger rise in peak junction temperature compared to that for a lower VDS (∼7.5 V) condition. The difference arises primarily due to reduction in the heat generating volume when operating under partially pinched-off (i.e., high VDS) conditions. Self-heating amplifies with this reduction as heating now takes place primarily over length scales less than the mean free path of the phonons tasked with energy dissipation. Being less efficient, the subcontinuum transport restricts thermal transport away from the device hot-spot causing a net increase in channel temperature. Taken together, even purely thermally driven device mean-time-to-failure is not, therefore, based on power dissipation alone as both bias dependence and subcontinuum thermal transport influence device lifetime.