Capacitance transient spectroscopy has been applied to identify deep levels associated with heteroepitaxial GaAs grown on silicon. Results from p+
n diode test structures reveal creation of the electron trap EL2 and a high density of hole states in the bandgap. This is the first reported observation of hole traps in MBE GaAs on Si. The activation behavior of the electron and hole signal peaks fits the signature of two different charge states associated with EL2, a native point defect complex seen in MOCVD, VPE, and bulk-grown GaAs, but not usually observed in MBE grown GaAs. Interstingly, the spectra seen show many similarities with earlier deep level transient spectroscopy (DLTS) observations on plastically deformed GaAs.