Arsenic can diffuse into high-κ dielectrics during GaAs-based metal oxide semiconductor transistor process,which causes the degradation of gate dielectrics.To explore the origins of the degradation,we employ nonlocal B3 LYP hybrid functional to study arsenic related defects in ZrO_2.Via band alignments between the GaAs and ZrO_2,we are able to determine the defect formation energy in the GaAs relative to the ZrO_2 band gap and assess how they will affect the device performance.Arsenic at the interstitial site serves as a source of positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs.Moreover,it is found that arsenic related defects produce conduction band offset reduction and gap states,which will increase the gate leakage current. Arsenic can diffuse into high-κ dielectrics during GaAs-based metal oxide semiconductor transistor process, which causes the degradation of gate dielectrics. To explore the origins of the degradation, we employ nonlocal B3 LYP hybrid functional to study arsenic related defects in ZrO_2.Via band alignments between the GaAs and ZrO_2, we are able to determine the defect formation energy in the GaAs relative to the ZrO_2 band gap and assess how they will affect the device performance. Arsenic at the interstitial site serves as a source of the positive fixed charge while at the oxygen or zirconium substitutional site changes its charge state within the band gap of GaAs. Moreover, it is found that arsenic related defects produce conduction band offset reduction and gap states, which will increase the gate leakage current.