不同氧化銦錫結構應用於氮化鎵垂直共振腔面射型雷射之研究

Abstract

本篇論文是在電機發混合式氮化鎵垂直共振腔雷射結構中，以30奈米厚度取代舊有一光學波長厚度的氧化銦錫層並探討其光性與電性的改善。首先，我們使用模擬軟體模擬不同厚度的氧化銦錫層對共振腔Q值的影響，由模擬的結果可知在沒有氧化銦錫層和有210奈米的氧化銦錫層的共振腔中Q值分別為3300及700；若換成30奈米厚，Q值僅會減少至3100，由此我們可預期用薄的氧化銦錫層能有效的提升共振腔的Q值。接著，在實驗中我們使用了四種不同元件的透明導電層，分別使用電子槍蒸鍍的30奈米與210奈米氧化銦錫層，還有利用離子濺鍍的30奈米結晶性和10奈米非晶性+20奈米結晶性氧化銦錫層。經由量測結果，30奈米厚的元件Q值約為1600，比起210奈米厚度的氧化銦錫層元件700高出了兩倍多。這樣的結果已能達到我們希望利用薄的氧化銦錫層去減少共振腔內光學損耗的目的。最後再比較四種氧化銦錫層應用於元件的特性。實驗結果顯示10奈米非晶性+20奈米結晶性氧化銦錫層的元件不僅具有最低的串聯電阻（165Ω）等電性表現外，其發光強度在電流孔徑所佔的比例更高達94%，此結果說明大部分的激發光都被侷限在設計的共振腔中，如此便能有效的降低產生雷射的臨界條件。在本論文中，我們不僅證實薄的氧化銦錫層可以有效提高元件的Q值，並且也找到一種最符合的氧化銦錫結構應用於我們的電機發面射型雷射上。

We have investigated the electrical and optical performance of GaN-based VCSELs with hybrid mirrors by four different ITO structures, especially in 30nm ITO layer instead of the traditional ITO layer of about 1λ thickness. First, by the simulation results, the qualify factors of the samples without ITO layer and with 210nm ITO layer were 3300 and 700, respectively. However, the sample with 30nm ITO layer was slightly decreased to 3100. It represents the thinner ITO layer can increase the qualify factor and reduce the internal loss of the cavity caused by the ITO layer in our devices. Then, we used four different ITO structures in our VCSELs including 30nm ITO film by e-gun, 210nm ITO film by e-gun, 30nm ITO film by sputter, and 10nm amorphous(α)-ITO film plus 20nm ITO film by sputter. Compared the VCSELs with four different ITO structures, the devices with 10nmα-ITO film plus 20nm ITO film by sputter has the lower serious resistance of about 165Ω and better optical confinement of about 94% in the aperture, and the quality factor of devices with 30nm ITO also has the higher quality factor of 1600. By the results, we can efficiently decrease the lasing threshold condition in our devices. In the report, we can not only increase the qualify factor but also obtain a better ITO structure used in our VCSELs. Finally, the VCSELs have the great potential to be the first electrical pumping GaN-based VCSELs with hybrid mirrors at room temperature.