Research Progress in Capping Diamond Growth on GaN HEMT: A Review

With the increased power density of gallium nitride (GaN) high electron mobility transistors (HEMTs), effective cooling is required to eliminate self-heating effect. Incorporating diamond into GaN HEMT an alternative way dissipate heat generated from active region. In this review, four main approaches for integration and are briefly reviewed, including bonding wafer together, depositing as a heat-dissipation layer on epitaxial or HEMTs, growth substrate. Due large lattice mismatch thermal mismatch, well crystal structure differences between GaN, all above works face some problems challenges. Moreover, review focused state-of-art polycrystalline nanocrystalline (NCD) passivation layers topside nucleation interface analysis, characterization, electrical performance HEMTs after film growth. Upon comparing three different methods electrostatic seeding most commonly used pretreatment method enhance density. NCDs usually grown at lower temperatures (600–800 °C) “gate growth” selective area emphasized. The influence quality dissipation capped analyzed. We consider that effectively reducing boundary resistance, improving regional interface, optimizing stress–strain state needed improve heat-spreading stability HEMTs. NCD-capped exhibit more than 20% operating temperature, current also improved, which shows good application potential. Furthermore, existing challenges have been discussed. characteristics itself discussed can completely explain diffusion effect corresponding technical problems.