Optoelectronic　devices,　such　as　light-emitting　diodes　(LEDs),　based　on　GaN-based　semiconductor　compounds　are　widely　used　for　their　advantages　of　long　life,　high　reliability,　and　low　energy　consumption.　The　persistent　challenge　is　integrating　LED　with　transistors　to　achieve　smaller　size,　lighter　weight,　higher　speed,　and　more　reliable　optoelectronic　integrated　circuits.　Here,　we　report　monolithically　and　vertically　integrated　LED-on-FET　devices　fabricated　on　a　novel　GaN　epitaxial　structure.　The　designed　device　structure　and　fabrication　process　are　simple.　It　also　eliminates　the　extra　area　occupied　by　the　transistor,　and　the　shared　n-GaN　layer　between　the　LED　and　FET　reduces　interconnect　resistance　and　improves　reliability.　The　measured　threshold　voltage　(　$\textit{V}_{\text{Th}}$　)　of　the　LED-on-FET　device　is　extrapolated　as　3.9　V　at　the　voltage　(　$\textit{V}_{\text{DD}}$　)　of　5　V,　and　　$\textit{V}_{\text{Th}}$　　decreases　with　the　increase　of　　$\textit{V}_{\text{DD}}$　.　More　importantly,　the　gate　voltage　(　$\textit{V}_{\text{GS}}$　)　shows　good　performance　in　modulated　electroluminescence　(EL)　intensity　and　switching　capability　of　the　LED.　The　integrated　LED　efficiently　emits　light　modulation　with　a　wavelength　of　440　nm　at　　$\textit{V}_{\text{DD}}$　　　$=$　　9　V　and　　$\textit{V}_{\textit{GS}}$　　　$=$　　4–9　V　(step　　$=$　　1　V),　which　are　necessary　for　devices　in　applications,　such　as　displays　and　smart　lighting.　This　epitaxy　structure　and　integration　scheme　is　promising　in　achieving　large-scale　optoelectronic　integrated　circuits,　such　as　the　next-generation　micro-LED　and　nano-LED　with　super　compact　integrated　drivers.　IEEE