Development of site-selective doping of rare-earth into nitride semiconductor

Eu掺杂氮化物半导体具有光谱窄、发光波长不受温度影响等特点，是一种很有希望实现新型器件的材料。然而，并不是所有的Eu离子纳入GaN主机是光学活性，导致发光效率的降低。这是由于Eu离子周围的局域晶体结构强烈影响能量传递和发光效率。本研究发现了镁共掺杂技术，并成功地通过控制光学位来提高发射效率。对于PL测量，观察到对应于^5D_0-^7F_2跃迁的三个强峰。随着Mg浓度的增加，主峰波长从622.3 nm变化到620.3 nm。最佳Mg掺杂浓度的样品的PL积分强度是未掺杂样品的20倍。对于最佳样品，发光效率估计为77%。这些结果表明Mg共掺杂可以控制GaN中的光学位，并导致从5D 0水平抑制非辐射分量。

Eu doped nitride semiconductor is a hopeful material for realizing a novel device with unique features, such as narrow spectra, and no temperature dependence of emission wavelength. However, not all Eu ions incorporated in GaN host are optically active, resulting in reduction of emission efficiency. This is due to that the local crystal structure around Eu ion strongly affects energy transfer and luminous efficiency. In this study, we found Mg codoping technology and succeeded to improve emission efficiency by controlling optical site. For PL measurement, three strong peaks corresponded to ^5D_0-^7F_2 transitions were observed. With increasing Mg concentration, the dominant peak wavelength changed from 622.3 to 620.3 nm. The PL integrated intensity of the sample with optimal Mg concentration was 20 times higher than that of the sample without Mg co-doping. For the optimal sample, the luminous efficiency was estimated to be 77%. These results indicated that Mg co-doping could control the optical sites in GaN and led to suppress the non-radiative component from 5D0 level.