Determination of channel temperature in AlGaN/GaN HEMTs grown on sapphire and silicon substrates using DC characterization method

Abstract

Self-heating effects and temperature rise in AlGaN/GaN HEMTs grown on silicon and sapphire substrates are studied, exploiting transistor dc characterization methods. A negative differential output resistance is observed for high dissipated power levels. An analytical formula for a source-drain current drop as a function of parasitic source resistance and threshold voltage changes is proposed to explain this behavior. The transistor source resistance and threshold voltage is determined experimentally at different elevated temperatures to construct channel temperature versus dissipated power transfer characteristic. It is found that the HEMT channel temperature increases rapidly with dissipated power and at 6 W/mm reaches values of 320 C for sapphire and 95 C for silicon substrate, respectively.

A Review of Raman Thermography for Electronic and Opto-Electronic Device Measurement With Submicron Spatial and Nanosecond Temporal Resolution

“…The equipment needed for these temperature assessments is available in standard electrical testing laboratories. Different methods are used, all based on measuring changes in temperature dependent electrical parameters, including: Saturated drain current [10][11][12][13][14]; gate leakage current and threshold voltage, among other parameters. These techniques offer no spatial resolution as such, but instead are sensitive to the entire periphery of the device channel [14].…”

Transient Thermoreflectance for Gate Temperature Assessment in Pulse Operated GaN-Based HEMTs

“…These properties include a high sheet carrier concentration, high mobility, and high critical electric field. High power applications require high power densities in the active region of these devices, which leads to highly localized Joule self-heating and potentially high peak temperatures [3,4]. Commercial applications now exist for GaN HEMTs, often operated in pulsed mode, although performance is typically de-rated for the purpose of thermal management and maintaining channel temperatures within a safe operating area, in particular, avoiding thermally activated degradation of the gate Schottky contact [5].…”

Measurement of Channel Temperature in GaN High-Electron Mobility Transistors

“…However, it is difficult to apply this technique to GaN devices due to degradation of the Schottky barrier with any sizeable gate current [6]. Using dc characteristics to measure channel temperature has also been proposed in GaN HEMTs [7], [8]. However, we have found that a dc measurement technique becomes problematic at high voltage because it can be cumbersome to remove the change in I D induced by current collapse in GaN HEMTs.…”