Luminescence of erbium implanted in various semiconductors such as Si, InP, GaAs, AlGaAs, GaInAsP, ZnTe and CdS is presented. The Er3+ emission wavelength is the same for all these semiconductors with a bandgap energy greater than the intrashell transition energy of Er 4f electrons (0.805 eV). The Er3+ emission intensity depends strongly on both the band gap energy of the host semiconductor and the material temperature. To obtain an intense room temperature emission, a wide-gap semiconductor must be used.