Reduced self-heating in ALGaN/GaN HEMTs using nanocrystalline diamond heat spreading films

Abstract

High electron mobility transistors (HEMTs) based on the AlGaN/GaN heterostructure are excellent candidates for power switching applications due to the high critical field of wide bandgap III-N materials. However, the reduction of drain current at high drain bias is a recognized device problem dominated by self-heating processes in power switching regimes [1]. Reducing HEMT channel temperature increases carrier mobility, decreases transition times, reduces switching losses, and ultimately improves converter efficiency. Despite the attractive thermal properties of CVD diamond as an integrated heat spreader, the thermal budget for fabricated HEMTs has limited the diamond deposition temperature in the past [2]. In this work, we present HEMTs with nanocrystalline diamond (NCD) heat spreading films, which offer a high thermal conductivity path only 50 nm away from the gate (k <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NCD</inf> of up to 1300 W/m-K).