| 摘要: | 此子計畫目的將會展示一種應用於紫外光和藍綠光波段以氮化鎵為材料的超高速、高輸出功率的新穎行波式光偵測器。並建立於紫外光波段測試元件的超高速光電量測平台，以分析元件在此操作波長下高輸出功率、高偏壓時的飽和行為。在工程和科學方面，藍光和紫外光波段的應用不勝枚舉，例如說: 低成本的塑膠光纖通信、衛星通信、國防工業上的飛彈追蹤和深海探測、化學/生化催化劑檢測、環保上的臭氧層破洞監控和檢測，等等..。這些應用在氮化鎵材料和其半導體雷射技術成熟後，其發展如雨後春筍般方興未艾。而能操作在紫外光和藍光波段，並同時具有低(背景)暗電流、高速、高效率，和高輸出功率的光偵測器在這些應用上，尤其是藍綠光通信方面，也扮演了關鍵性的腳色。使用氮化鎵材料系統作為此波段的光偵測器和一般能帶寬度遠小於紫外光光子能量的材料(Si, GaAs, InP)相比之下其具有無數的優點。例如說: 可和氮化鎵雷射或發光二極體單晶積體化結合，較高的響應度(以GaAs p-i-n 偵測器為例，在此波段入射光會在p 或n 表面被完全吸收、復合，無法在高電場的 i 區域產生，因此造成了低響應度。) ，較高的操作速度 (無p, n 區域擴散電流問題) ，較強的環境變異忍受能力，和較高的輸出功率。此子計畫中我們將結合在InP 或GaAs 材料系統中超高速行波式光偵測器的設計概念和氮化鎵一些特別的材料光電特性，成功製作出可操作在波長~500nm(藍綠光)和 ~270nm(紫外光)，超高速(~20GHz)，高響應度(>0.2A/W) 的側邊入射式p-i-n 行波式氮化鎵光偵測器。側射式光偵測器結構，為增進偵測器頻寬-效率乘積最有效的方法。在氮化鎵光偵測器的發展過程中，到目前為止此結構並未有任何文章發表。除此之外我們也將利用特別磊晶層結構解決InGaN/GaN 壓電場和外加電場反向和 p-type GaN 高電阻的問題，以降低元件操作電壓和增進元件操作速度。我們將同時採用可調式半導體雷射互擊(Heterodyne Beating )和鎖模雷射倍頻所產生紫外光波段的短脈衝光源，以量測元件的超快頻域和時域表現。並藉此來分析此元件在紫外光波段激發下，高功率連續操作的電頻寬表現和飽和行為。此計畫的成功將為氮化鎵化合物半導體帶來全新商品化的機會和市場，並可更清楚瞭解到氮化鎵材料系列中的載子動力學。 In this sub-project, we will demonstrate a novel III-nitride based traveling-wave photodetectors with high bandwidth-efficiency and bandwidth-saturation power products performances for blue-green and ultraviolet (UV) wavelengths applications. We will establish ultra-high speed optoelectronic measurement systems to test and analyze the saturation behaviors of demonstrated devices under high dc bias voltage operation and high optical power illumination. There are several scientific and engineered applications in the blue-green and ultraviolet wavelengths regimes, such as, low cost plastic fiber communication, space-based optical communication, missile tracking and intercept, biological and chemical agent sensing, and ozone-hole sensing. These applications are growing up significantly due to the maturity of GaN based material and semiconductor laser. High speed p-i-n photodetectors in the UV and blue-green wavelength regimes, with low dark (background) current, high efficiency, and high saturation power performance, play important role in these applications, especially for optical communication. Compared with p-i-n photodetectors (PDs), which are made of GaAs, Si, or InP, under UV wavelength illumination, III-nitride based PDs have the capability to be monolithic integrated with GaN laser and can eliminate the concentration of photo-absorption process and photo-generated carriers at the topmost p or n cap epi-layer. The concentration of photo-generated carriers at p or n regions will cause serious bandwidth and efficiency degradation. Furthermore, III-nitride based PD can be operated in harsh environment and have high output saturation power due to its relative large bandgap. In this sub-project, we will incorporate the design concepts of InP based ultra-high speed photodetectors and some unique properties of III-nitride based materials to successfully demonstrate edge-coupled traveling wave photodetectors, which can be operated under blue-green (~500nm) and UV (~270nm) wavelength regimes, with high responsivity (>0.2A/W), high saturation power, and ultra-high speed performance (~20GHz). We will adopt the heterodyne beating and multiplying frequency techniques of mode-locked Ti:sapphire laser to measure the frequency response and time domain impulse response of fabricated TWPDs, respectively. Through the use of these techniques, we can get the electrical bandwidth of fabricated device under low and high optical power illumination precisely. The success of this project will bring a new market for nitride-based compound semiconductors and can understand the ultra-fast carrier dynamic in III-nitride based materials more clearly. 研究期間：9308 ~ 9407 |
