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

稀土（RE）掺杂半导体作为一种很有前途的新型材料受到了极大的关注，它通过电注入的方式从稀土壳层发射光，其中电子-空穴对的能量被转移到稀土壳层。RE离子的4f壳层跃迁会产生尖锐的发射线，其波长在很大程度上与宿主材料和温度无关。这种稳定性的发生是因为填充的外层5s和5p电子壳层屏蔽了与宿主相互作用的内层4f电子壳层的跃迁。Er^<3+>离子在1.5 μm左右从第一激发态（^4I_<13/2>）到基态（^4I_<15/2>）的内部4f壳层跃迁特别有趣，因为波长与光通信中使用的硅纤维的最小损耗区域相匹配。在本课题中，我们研究了Er，O共掺GaAs （GaAs:Er，O）的新型极稳定波长发光器件，为进一步提高其性能提供了线索。实验结果如下：1)室温注入电流，在GaInP/GaAs:Er，O/GaAs双异质结构中观察到Er相关发光。EL谱以Er-2O谱线为主，说明Er-2O中心形成成功，电流注入优先激发了中心。2) EL强度与电流密度的关系表明，电流注入的Er离子激发截面非常大，约为10^<-15> cm^2。通过时间分辨的EL强度测量证实了大的激发截面。它比掺铒的Si led （6 × 10^<-17> cm^2）大两个数量级。3)利用泵浦和探针反射技术在皮秒时间尺度上研究了砷化镓中的Er，O载流子动力学。时间分辨反射率呈特征倾角；在小于1ps时急剧下降到负值，然后在大于100ps时增加。初始阶段的反射率增加由两个分量组成，强烈依赖于Er浓度。Er浓度对组分的依赖性表明，最初更快的衰减是由于Er和O共掺杂Less诱导的陷阱捕获了非平衡载流子

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