| 摘要: | 資料中心和其光纖連接網路建設的普及化就如同19世紀時電力網路建設一般，正在為人類的文明帶來新一波的革命。在此種光網路中因為機房中多達百萬條的短傳輸距離(< 2 km)的光纖通道數，所以能夠低功耗、高密度、小體積(form factor)、封裝的光收發模組為現今發展的一重要趨勢。在接收模組中為了能夠進一步縮小體積和降低成本，將用於把入射光聚焦於光偵測器的透鏡移除為一有效的方法。然而為了能夠滿足下世代 400和800 Gbit/sec乙太網路的頻寬需求，光偵測器需要的3-dB光電轉換頻寬必須大於30 GHz，而且響應度也要滿足0.7 A/W以上，如此使得元件的主動區面積受到嚴格限制很難拉大，這也讓沒有透鏡的耦光過程變得十分困難。除此之外，此種光偵測器也必須能夠使用轉阻放大器所提供的低偏壓(< -2V)操作以減少偏壓電路的所占的封裝空間。 在此計畫中，我們將利用一種我們所展示的新穎單載子光偵測器來滿足上述的所有需求。我們使用了Type-II p- GaAs0.5Sb0.5/i- In0.53Ga0.47As 的吸收層來取代了傳統單載子光偵測的p-In0.53Ga0.47As吸收層。由於 Type-II介面能隙只有0.5 eV比In0.53Ga0.47As能隙(0.75 eV)來的窄，所以能夠在給定的吸收層厚度下有效增強吸收，提升響應度表現。從另一方面來看，我們此種光吸收層也可以在給定的響應度條件下有效減少其厚度，並縮短載子傳輸時間，提升元件速度。此外為了解決無透鏡封裝和低偏壓操作的問題，我們會利用較厚的InP集極層厚度和電子較快的漂移速度來增加元件光窗面積減少頻寬劣化以利正面直接耦光。我們也會考慮經過光纖斜切面的形變輸出光場，並最佳化偵測器光窗形狀以降低耦和損耗。除此之外我們更會嘗試使用覆晶式封裝，並在基板用半導體製程製作一透鏡以利耦光。 綜上所述，我們將會結合上述學校的新元件技術和索爾思公司所將支援的先進封裝技術，來展示可應用於400 (800) Gbit/sec乙太網路且具有高線性度、高靈敏度、高速和高可靠度且低成本的光接收模組。 ;The construction of of data center and the fiber communication network as its backbone are both booming in the recent 10 years. This case is just similar with the birth of electrical network at 19th century, which results in the revolutionary change in human’s civilization. In the cabins of data center, the essential number of short reach (<2 km) optical interconnect (OI) channels is up to several millions. This drives us to develop the low power consumption, densely packaged, small form factor transreceiver modules to meet the above-mentioned requirements. Removing the lens inside ROSA package is one of the most effective ways to further minimize the size and reduce the cost of receiver optical sub-assembly (ROSA). However, in order to meet the bandwidth requirement in next generation 400 and 800 Gbit/sec Ethernet, the optical-to-electrical (O-E) bandwidth of photodetector (PD) inside ROSA must be over 30 GHz and have a responsivity value >0.7 A/W. These specifications seriously limit the enlarging of active area of photodetector and let the lens-free alignment become very difficult. Besides, in order to save the space of dc bias circuit in ROSA package, such kind of PD must be able to function under the low reverse bias voltage (< -2V), which is supplied by the integrated trans-impedance amplifier (TIA). In this project, we will develop our newly demonstrated uni-traveling carrier photodiodes (UTC-PDs) to satisfy the above-mentioned requirements in PD. The traditional p-type In0.53Ga0.47As absorber inside UTC-PD is replaced by the Type-II p- GaAs0.5Sb0.5/i-In0.53Ga0.47As hetero-structure. Due to that the bandgap of type-II interface is narrower than that of In0.53Ga0.47As (0.5 vs. 0.75 eV) absorber, so it can effectively enhance the photo-absorption process and responsivity performance in a given absorption layer thickness. On the other hand, for the case of a desired responsivity, this novel design of absorber can reduce its thickness, shorten the carrier transit time, and enhance the speed performance. By combing such absorption layer with a thick InP collector layer with only electron as active carrier, we can thus increase the diameter of active window of PD for top-side alignment and minimize the degradations in O-E bandwidth and responsivity. Furthermore, we will consider the deformation of optical beam after passing the beveled optical fiber tip and further optimize the shape of active PD mesa to minimize the coupling loss. The approach of flip-chip bonding package integrated with a InP substrate lens for lens-free backside alignment will also be realized in such PD structure. Overall, by combing with the above-mentioned device technology with advanced package technology, which is supported by Source Photonic Company, we will demonstrate a high-linearity/-sensitivity-/ and reliable PD based photo-receiver module with low-cost for next-generation (400) 800 Gbit/sec Ethernet communication system. |
