SUMMARY

The fields of power and radio frequency (RF) electronics have experienced tremendous growth over recent years as gallium nitride (GaN) device technology is maturing. GaN high electron mobility transistors (HEMTs) are particularly well-suited for high-power and high-frequency applications due to their excellent sheet charge density and channel mobility, and the large bandgap energy of GaN. However, GaN HEMTs suffer from acute self-heating that limits their performance in high-power and high-frequency applications. The most recent advancements in GaN HEMT device-level thermal management consist of integrating high-thermal conductivity CVD diamond substrates to GaN HEMT device layers (GaN-on-diamond technology). While the thermal merits for CVD diamond substrate integration are clear, the structural integrity and reliability of GaN-on-diamond HEMTs requires further investigation. To study the structural impact that CVD diamond integration has on GaN HEMTs, GaN-on-diamond materials fabricated by various techniques have been examined via optical stress metrology techniques. Ultra-wide bandgap (UWBG) aluminum gallium nitride (AlGaN) HEMTs have the potential to exceed the performance limitations of GaN HEMTs for the next generation of power and RF electronic device technologies. The acute self-heating challenges for high-power GaN HEMTs are exacerbated for AlGaN HEMTs because the thermal conductivity of AlGaN is an order of magnitude lower than that of GaN. The low thermal conductivity of AlGaN increases the device thermal resistance of AlGaN HEMTs and changes the transient thermal dynamics of AlGaN HEMTs under pulsed-mode operation. Therefore, AlGaN HEMT devices require novel device-level thermal management solutions to realize their theoretical performance potential. To address the thermal management challenges, novel device-level thermal management approaches have been identified via thermal finite element analysis (FEA) and in situ junction temperature experiments.