Time-dependent thermal crosstalk in multifinger AlGaN/GaN HEMTs and implications on their electrical performance

The thermal dynamics of multifinger AlGaN/GaN high electron mobility transistors (HEMTs) with varying gate pitch was investigated using time-resolved Raman thermography. An identical temperature rise was measured in all gate fingers within the first ∼500 ns duration of electrical pulses. Gate finger temperature differences only emerge after 500 ns, due to the onset of thermal crosstalk. This thermal crosstalk onset delay is attributed to the finite rate of heat diffusion between gate fingers. Reducing the device gate pitch was found to increase the magnitude of transient thermal crosstalk. Implications of each gate finger within a multifinger HEMT having a different transient temperature are discussed in the context of device characteristics. The experimental results are compared to time-domain three-dimensional finite difference heat diffusion simulations.

Research highlights
► Transient thermal crosstalk measured in pulse-operated multifinger AlGaN/GaN HEMTs.
► Inter-finger heat diffusion was found to be negligible within the first 500 ns of electrical pulses.
► At 3 μs after turn-on, thermal crosstalk significantly affects devices with gate pitch <40 μm.
► Gate pitch should be optimised to minimize transient thermal cross-talk.