我們提出了新穎的分離式傳輸復合行波式光二極體以及最佳化吸光區設計之高速單載子傳輸光二極體，此二種光二極體不但可提升光二極體的輸出功率-頻寬雙重表現，更可解決傳統光二極體在設計上載子傳輸時間、本質電容以及飽和電流三者的抵觸關係。高速光二極體通常追求頻寬與飽和電流的表現，但傳統的光二極體在高功率操作下，會因載子漂移累積，產生空間電荷遮蔽效應，造成嚴重的頻寬限制與輸出功率衰退的缺點。我們針對傳統光二極體所遭遇到的問題，提出了新穎的磊晶結構加以克服。1.分離式傳輸復合光二極體:在傳統pin光二極體的吸光層中，加入一部分的復合中心(低溫成長砷化鎵)與傳輸層(砷化鎵)做組合。和傳統光二極體相比之下，除了將可提高速度與輸出功率表現外，更解決了傳統光二極體在設計上的抵觸問題。2.最佳化吸光區設計之高速單載子傳輸光二極體:在p-type吸光區做最佳化的掺雜濃度設計，使內部感應電場增大，讓電子能以最快速度傳輸，同時兼顧量子效率。此二種元件的成功，可應用在光通訊850nm波段以做為一兆赫波源發射器上的光電導元件，提供作為一穩定的兆赫波源發射器。 In this paper, We demonstrate the high-speed and high-power performance of separated-transport-recombination photodiodes (STR-PDs) under continuous-wave operation. As compared to the control without recombination center, STR-PD has superior bandwidth performance under higher output photocurrent without sacrificing responsivity seriously. We introduce a GaAs/AlGaAs based Unitraveling Carrier Photodiode (UTC-PD) for a wavelength of around 830nm. There is significant bias and output current dependent bandwidth enhancement phenomena observed with this device. According to our microwave and optical-to-electrical (O-E) measurement results, such distinct phenomena can occur under a much lower current density (0.3mA/μm2 vs. 0.05mA/μm2) than previously reported for InP-InGaAs UTC-PDs. This can be attributed to the self-induced field in the absorption region, made possible due to the optimized p-type doping profile.
