Lateral　gallium　nitride　(GaN)-based　high-electron-mobility　transistor　(HEMT)　power　devices　have　high　current　density,　high　switching　speed,　and　low　on-resistance　in　comparison　to　the　established　silicon　(Si)-based　semiconductor　devices.　These　superior　characteristics　make　GaN　HEMTs　ideal　for　high-frequency,　high-efficiency　power　conversion.　Using　efficient　GaN　HEMT　devices　switched　at　high　frequency　in　power　electronic　systems　could　lead　to　an　increase　in　power　density　as　well　as　a　reduction　in　the　weight,　size,　and　cost　of　the　system.　However,　conventional　packaging　configurations　often　compromise　the　benefits　provided　by　high-performance　GaN　HEMT　devices,　for　example,　by　increasing　the　parasitic　inductance　and　resistance　in　the　current　loops　of　the　device.　This　undesirable　package-induced　performance　degradation　is　prominent　in　the　cascode　GaN　device,　where　the　combination　of　a　high-voltage　depletion-mode　GaN　semiconductor　and　low-voltage　enhancement-mode　Si　semiconductor　is　needed.　In　this　study,　a　new　package　is　introduced　for　high-voltage　cascode　GaN　devices　and　is　successfully　demonstrated　to　make　the　device　more　suitable　for　megahertz　operation.　This　packaging　prototype　for　cascode　GaN　devices　is　fabricated　in　a　power　quad　flat　no-lead　format　with　the　new　features　of　a　stack-die　structure,　embedded　external　capacitor,　and　flip-chip　configuration.　The　parasitic　ringing　in　hard-switching　turn-off　and　switching　losses　in　soft-switching　transitions　are　both　effectively　reduced　for　this　newly　packaged　device　compared　with　a　traditional　package　using　the　same　GaN　and　Si　devices.　Improved　thermal　dissipation　capability　is　also　realized　using　this　new　package　for　better　reliability.