自旋電子流自鎳薄膜及四氧化三鐵奈米球注入至氮化銦鎵/氮化鎵奈米柱光電半導體之研究

Abstract

本論文的動機乃欲比較傳統薄膜自旋半導體與奈米柱結構自旋半導體的輻射旋光度(Degree of circularly polarized light)的表現優劣。實驗上主要利用光激螢光(PL)與電激螢光(EL)方法來研究三─五族(氮化銦鎵/氮化鎵)奈米柱半導體所構成的自旋光電半導體的輻射旋光度於外加磁場下的變化，並再附著磁性奈米球 (四氧化三鐵)於奈米柱的孔隙中進而影響輻射旋光度。 當薄膜多重量子井被蝕刻為奈米柱多重量子井時，由於內建電場大幅縮小、侷限位勢亦趨向對稱，使得量子侷限史塔克效應(QCSE)消失，進而降低量子井內的快速自旋弛豫，同而增加載子自旋同調時間。另外，磁性奈米球的加入造成自旋閥效率提升。因載子自旋同調時間和自旋閥效率一併提升，本文研究顯示於常溫低磁下，吸附了磁性奈米球的奈米柱自旋光電半導體的輻射旋光度達10%以上並遠遠大於同樣材料的薄膜自旋半導體。並且其常溫低磁的條件也遠優於具備相同輻射旋光度之自旋半導體。

The motivation of this thesis is to compare the performance of the degree of circularly polarized light between conventional thin film spin-LED and nanorod spin-LED. In our experiment, we compare the degree of circularly polarized light for the thin film and nanorod spin-LEDs, which is composed of InGaN/GaN multiple quantum wells, under an external magnetic field by photoluminescence and electroluminescence. We also deposit the Fe3O4 nanoparticles into the space between nanorods in order to enhance the degree of circularly polarized light arising from nanorod spin-LED. The quantum confined stark effect will gradually vanish and confined potential will become more symmetric as the thin film multiple quantum wells are etched into the nanorod structure. Thus the spin coherent time will become longer in quantum well. In addition, the efficiency of spin valve will increase after the deposition of Fe3O4 nanoparticles. Due to the increment for both the spin coherence time and efficiency of spin valve, our results show that the degree of circularly polarized light of the nanorod spin-LED with Fe3O4 nanoparticles under low external magnetic field and room temperature can be more than 10%. Its excellence performance and practical working condition make nanorod spin-LED becomes a potential spin device.