High-quality　bonding　of　4-inch　GaAs　and　Si　is　achieved　using　plasma-activated　bonding　technology.　The　influence　of　Ar　plasma　activation　on　surface　morphology　is　discussed.　When　the　annealing　temperature　is　300　℃,　the　bonding　strength　reaches　a　maximum　of　6.2　MPa.　In　addition,　a　thermal　stress　model　for　GaAs/Si　wafers　is　established　based　on　finite　element　analysis　to　obtain　the　distribution　of　equivalent　stress　and　deformation　variables　at　different　temperatures.　The　shape　variation　of　the　wafer　is　directly　proportional　to　the　annealing　temperature.　At　an　annealing　temperature　of　400　℃,　the　maximum　protrusion　of　4　inches　GaAs/Si　wafers　is　3.6　mm.　The　interface　of　GaAs/Si　wafers　is　observed　to　be　dense　and　defect-free　using　a　transmission　electron　microscope.　The　characterization　of　interface　elements　by　X-ray　energy　dispersion　spectroscopy　indicates　that　the　elements　at　the　interface　undergo　mutual　diffusion,　which　is　beneficial　for　improving　the　bonding　strength　of　the　interface.　There　is　an　amorphous　transition　layer　with　a　thickness　of　about　5　nm　at　the　bonding　interface.　The　preparation　of　Si-based　GaAs　heterojunctions　can　enrich　the　types　of　materials　required　for　the　development　of　integrated　circuits,　improve　the　performance　of　materials　and　devices,　and　promote　the　development　of　microelectronics　technology.　©　2024　Chinese　Institute　of　Electronics.