Transient thermal characterization of HEMT devices

Hetero junction Bipolar Transistor (HBT) and High Electron Mobility Transistor (HEMT) arrays are commonly used for RF and microwave high speed and high power applications. Thermoreflectance imaging can be utilized to understand the transient thermal characteristics of a GaN HEMT device. A time resolution of 50 ns clearly shows the thermal location-dependent time constants for the device, which could be used for further analysis of the thermal structure. An array of GaAs HEMT devices on a Monolithic Microwave Integrated Circuit (MMIC) is also characterized to gain an understanding of the local thermal resistance distribution in comparison to a finite element analysis. Since thermoreflectance is sensing the light reflectance of the surface, hotspots underneath opaque layer(s) is discussed to illustrate the utilization of this method for such devices.