Due　to　the　superior　thickness-dependent　properties,　2D　materials　have　exhibited　great　potential　for　applications　in　next-generation　optoelectronic　devices.　Despite　the　significant　progress　that　has　been　achieved,　the　synthesis　of　2D　AlN　remains　challenging.　This　work　reports　on　the　epitaxial　growth　of　2D　AlN　layers　via　utilizing　physically　transferred　graphene　on　Si　substrates　by　metal-organic　chemical　vapor　deposition.　The　2D　AlN　layers　sandwiched　between　graphene　and　Si　substrates　are　confirmed　by　annular　bright-field　scanning　transmission　electron　microscopy　and　the　effect　of　hydrogenation　on　the　formation　of　2D　AlN　layers　is　clarified　by　theoretical　calculations　with　first-principles　calculations　based　on　density　functional　theory.　Moreover,　the　bandgap　of　as-grown　2D　AlN　layers　is　theoretically　predicted　to　be　approximate　to　9.63　eV　and　is　experimentally　determined　to　be　9.20-9.60　eV.　This　ultrawide　bandgap　semiconductor　shows　great　promise　in　deep-ultraviolet　optoelectronic　applications.　These　results　are　expected　to　support　innovative　and　front-end　development　of　optoelectronic　devices.