Intracenter transitions in triply ionized erbium ions diffused into III‐V compound semiconductors

The rare‐earth element, erbium (Er), was successfully diffused into GaAs and InP for the first time. Two intense and three weak sharp photoluminescence (PL) lines related with Er were observed at a wavelength of ∼1.55 μm both in GaAs and InP. It was found, for the first time, that the emission energy and the linewidth of the two intense Er‐related PL lines do not depend on temperatures up to 220 K. This clearly indicates that these sharp emission lines are due to 4f‐intracenter transitions in triply ionized erbium (Er³⁺) ions, and that the 4f orbitals are well shielded from a crystal field by the outer closed orbitals. Furthermore, it was found that the intensity ratio of the five emission lines from Er³⁺ is independent of the excitation power density. The results reveal that the Er³⁺ ion substitutes a cation site both in GaAs and InP, and that the five PL lines correspond to the transitions from the first excited state to the five crystal‐field‐split ground states of Er³⁺ ion with a tetrahedral (T_d) symmetry.