Investigation for improved performance of new-type extremely-stable-wavelength light-emitting devices based on rare-earth-doped III-V semiconductors

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Rare-earth (RE) doped semiconductors have gained significant attention as a promising new class of materials that emit light from the RE 4f shell by means of electrical injection, in which the energy of electron-hole pairs is transferred to the RE shell. The intra-4f shell transitions of RE ions give rise to sharp emission lines whose wavelengths are largely independent of both the host materials and temperature. This stability occurs because the filled outer 5s and 5p electron shells screen transitions within the inner 4f electron shell from the interaction with the host. The intra-4f shell transitions from the first excited state (^4I_<13/2>) to the ground state (^4I_<15/2>) of Er^<3+> ions at around 1.5 μm is of special interest because the wavelength matches the minimum loss region of silica fibers used in optical communications.In this research project, we investigated new-type extremely-stable-wavelength light-emitting devices with Er,O-codoped GaAs (GaAs:Er,O) to get a clue for … More their improved performance. Results obtained experimentally are summarized as follows :1) Er-related luminescence was observed in GaInP/GaAs:Er,O/GaAs doubleheterostructures by injecting current at room temperature. The EL spectrum was dominated by Er-2O lines, suggesting a successful formation of the Er-2O center and preferential excitation of the center by current injection.2) The current density dependence of the EL intensity revealed an extremely large excitation cross section of Er ions by current injection, approximately 10^<-15> cm^2. The large excitation cross section was confirmed by time-resolved measurements of the EL intensity. It is by two orders in magnitude larger than that of Er-doped Si LEDs (6 x 10^<-17> cm^2).3) Carrier dynamics in GaAs:Er,O were investigated in a picosecond time scale by a pump and probe reflection technique. Time-resolved reflectivity exhibited a characteristic dip ; a steep decrease to negative in less than 1 ps and then an increase in more than 100 ps. The reflectivity increase at the initial stage, consisting of two components, depended strongly on Er concentration. The Er-concentration dependence on the components reveals that an initial faster decay is due to the capture of nonequilibrium carriers by a trap induced by Er and O codoping Less