氮化鎵面射型雷射製程技術之研究

Abstract

本論文主要是探討兩種改善氮化鎵微共振腔元件特性的製程技術。以期能夠成功製作出電激發氮化鎵面射型雷射。其中一種改善的方法是用ITO來取代過去氮化鎵微共振腔元件的Ni/Au薄金屬透明電極.我們首先利用模擬軟體來計算出ITO所需的厚度並充分運用各種半導體製程技術，諸如：蝕刻、薄膜成長、歐姆接觸電極之蒸鍍等…，成功的製作出利用ITO作為透明電極的氮化鎵微共振腔元件。此一元件在室溫10毫安培的電流注入下，發光波長在458nm，並具有一窄的光譜半高寬值為2nm。由此元件的光學特性可以計算出此元件的Q值已經由過去元件的68增加到229.此結果告訴我們在製作high Q的光學元件時，透明電極的吸收率扮演著極重要的角色。除此之外，我們也針對元件發光孔內的亮點去做探討。可以發現這些亮點相對於其他區域都有著比較高的Q值。並且在其中一處發現了Q值高達894的亮點。由雷射理論我們可以推斷出這些亮點是由於氮化鎵/鋁化鎵布拉格反射鏡的不均勻造成的。另外一個製程技術是利用鎂離子佈值在p型氮化鎵來取代過去利用氮化矽絕緣層作為電流侷限的方法。我們首先利用模擬軟體來設計鎂離子佈值的能量及所需的氮化矽緩衝層的厚度。並且由二次離子質譜儀的結果來加以確定。從元件進行複合式結構的氮化鎵面射型雷射之設計。由元件發光的情形可以看出我們徹底解決了過去利用氮化矽絕緣層所造成的漏電流的問題。上述兩種製程技術的改善說明了其發展電激發氮化鎵面射型雷射之可行性與潛力。

In this thesis, we investigate the performance of GaN based micro-cavity light emitting diode (MCLED) with two fabrication techniques for the realization of electrically injected GaN VCSEL. One of the techniques is the use of high-transmittance transparent contact, ITO film. The device shows the turn on voltage is a comparable value with Ni/Au device to be about 3.4V and 530Ω, respectively. The emission peak wavelength of the ITO MCLED was located at 458nm with a narrow line-width of 2nm. Compared to the emission spectrum of the conventional Ni/Au MCLED, the ITO MCLED shows a relatively excellent line-width and possesses a high Q factor of about 229. The improvement of Q factor shows that the non-absorbed transparent contact indeed plays an important role to fabricate this kind of high Q device like VCSEL. Moreover, the “bright spots” within the emission aperture were also discussed. We found the Q factors at the bright spots are relatively higher than those within the dark regions, even as high as 894. The excellent Q factor is the best value compared with that of MCLED published in the recent literatures. The other technique is current confinement using Mg ion implantation. The device is implanted by 80keV Mg with does of 2E15. Moreover, 100nm thick SiNx as buffer layer is required for avoiding damage induced defect in MQWs. The absence of side wall emission of implanted MCLED not only confirms the existence of leakage current in our conventional device but also verifies the current confinement was successful. Such techniques could be the basis for electrically injected GaN-based VCSEL.