Thermal characterization of high power transistor arrays

Thermal performance is an important factor in the design of power devices. Previous studies have shown that nonuniform temperature distributions occur in both small transistors [1,2,3] and in large area power transistor devices [4,5,6]. We present extensive thermal characterization of large scale transistor arrays that are typical in power applications. Thermal images using the thermoreflectance technique as well as thermocouple data are presented for the device under both low and high current conditions. Thermal characterization is obtained for load currents up to 4 amperes and current densities up to 45 A/mm² in the power arrays. Temperature nonuniformity in the arrays is studied as a function of array size, bias level, and ambient temperature. Increased heating is shown to develop near the source contact region in the arrays.