| 摘要: | 在本論文中，我們展示了多種用於下世代乙太網系統的高速雪崩二極體/光電二極體。其中之一是一個具有 type-II 型 GaAs0.5Sb0.5 (p)/In0.53Ga0.47As (i) 混合吸收層的單載子傳輸光電二極管 (UTC-PD)，這種設計可進一步提高 UTC-PD 的帶寬效率乘積。在我們提出的新 UTC-PD 結構中，p型 In0.53Ga0.47As 吸收層被 type-II 型 GaAs0.5Sb0.5 (p)/In0.53Ga0.47As (i) 混合型吸收層取代。由於 GaAs0.5Sb0.5 和 In0.53Ga0.47As 層之間界面處的能隙變窄和光吸收過程的增強，與具有相同厚度(0.7 μm)的純 In0.53Ga0.47As 吸收層和零光耦合損耗的 UTC-PD 相比，我們的元件的響應率提高了 16.7% 以上。我們展示的具有簡單頂部(正面)照明結構的元件具有大型的主動平台 (25 μm)，在1.31 µm 光波長下，具有寬大的光電 (O-E) 帶寬 (33 GHz)、高響應度 (0.7 A/W) 和高飽電流 (>5 mA)。用倒裝晶片技術貼合基板透鏡並封裝的集成以及Rx在DR-4系統中的應用。我們的封裝方式讓這種元件無需使用任何外部透鏡即可實現極高的響應度 (0.95 A/W)、寬大的 O-E 帶寬 (33 GHz)、高飽和電流 (4 mA) 和高靈敏度 (-10 dBm OMA)。由於這種接收器沒有內部增益，因此需要強大的光學本地振盪器 (LO) 功率泵浦來處理自外差差拍裝置上的弱接收信號。為了克服上述問題，我們展示了一種基於 In0.52Al0.48As 的新型頂照(正照)式雪崩光電二極管 (APD)。
透過結合組合電荷層設計與特殊的 p 極面朝上蝕刻平台結構，將該 APD 的倍增 (M-) 層外圍(邊緣)的電場歸零，從而消除邊緣崩潰的現象。這導致我們的 APD 特性同時具備高速、高飽和功率、高響應度和低暗電流的特性，這對於高性能相干接收器應用是非常重要的。這個元件具有簡單的頂部(正面)收光結構，具有寬大的光電 (O-E) 帶寬 (21 GHz)、高響應率（0.9 Vbr 時為 5.5 A/W）和高達 8 mA 的飽和電流，且元件的有效直徑為 24 μm，這有便於光學對準。此外，自外差差拍裝置中的波長掃描激光器的非線性驅動可以產生類似波形的光脈衝序列，提供高達 158% 的有效光調製深度，從我們的 APD中產生最大光生射頻功率高達 +5.5 dBm（在10 GHz）。此外，為了滿足下世代乙太網系統的帶寬要求，我們需要 100G 的 APD。我們展示了一種具有 In0.52Al0.48As 倍增 (M-) 層的新型垂直照明雪崩光電二極管 (APD)。堆疊式的累增(M-)層設計與獨特的 p 極面朝上的平面結構結合，可以放寬增益帶寬積和暗電流之間的基本權衡。這導致我們的 APD 同時具有高響應度、高速、高飽和功率和低暗電流的特性。在大約 0.9 Vbr 的偏壓下操作時，所展示的元件具有簡單的頂部照明結構和 14 (24) μm 的大活動窗口 (平台) 直徑，表現出高響應率 (2.23 A/W)、寬大的光電帶寬 (30 GHz)、大增益帶寬積 (270 GHz)、低暗電流 (~200 nA) 和高達 11 mA 的飽和電流。為了進一步提高增益帶寬積 (GBP)，我們將具有 14μm 窗口直徑的APD進行倒裝晶片貼合，使這個元件在 0.9Vbr 下具有寬帶寬 (36GHz)、高響應度 (3.4A/W)、低暗電流 (175nA) 、高 MMW輸出功率（40GHz 時為 -1dBm）和高飽和電流(12.5mA)。這種 APD 結構的卓越特性為進一步提高相干通信或 106 Gbit/sec PAM-4 應用的接收器靈敏度性能打開了新可能。
;In this thesis, we demonstrated various types of High-Speed Avalanche photodiodes/Photodiodes (PDs) for Next generation ethernet system. One of them uni-traveling carrier photodiode (UTC-PD) with type-II GaAs0.5Sb0.5 (p)/In0.53Ga0.47As (i) hybrid absorber for further enhance the bandwidth-efficiency product of UTC-PD. In our proposed new UTC-PD structure, the p-type In0.53Ga0.47As absorption layer is replaced by the type-II GaAs0.5Sb0.5 (p)/In0.53Ga0.47As (i) hybrid absorber. Due to the narrowing of the bandgap and enhancement of the photo-absorption process at the type-II interface between the GaAs0.5Sb0.5 and In0.53Ga0.47As layers, our device shows an over 16.7 % improvement in the responsivity as compared to that of UTC-PD with the same thickness of pure In0.53Ga0.47As absorber (0.7 μm) and a zero optical coupling loss. Our demonstrated device with a simple top-illuminated structure offers a large active mesa (25 μm), a wide optical-to-electrical (O-E) bandwidth (33 GHz), a high responsivity (0.7 A/W), and a high saturation current (>5 mA) under 1.31 µm optical wavelength. Integration with a substrate lens for flip-chip bonding package and the application of Rx in DR-4 system. Such device can achieve a very-high responsivity (0.95 A/W), wide O-E bandwidth (33 GHz), high saturation current (4 mA), and high-sensitivity (-10 dBm OMA) without using any external lens in our package.Since this kind of receiver doesn’t have internal gain, therefore it requried strong optical local-oscillator (LO) power pumping to process the waek receive signal on the self heterodyne beating setup.In order to overcome the aforementioned isuse, a novel In0.52Al0.48As based top-illuminated avalanche photodiode (APD) is demonstrated. By combining the composite charge-layer design with a special p-side up etched mesa structure to zero the electric (E)-field at the periphery of this APD’s multiplication (M-) layer, the edge breakdown phenomenon can be eliminated. This in turn leads to the simultaneous high-speed, high-saturation-power, high responsivity, and low-dark current performance of our APDs characteristics, which are essential for high-performance coherent receiver applications. The demonstrated device with its simple top-illuminated structure exhibits a wide optical-to-electrical (O-E) bandwidth (21 GHz), high responsivity (5.5 A/W at 0.9 Vbr), and saturation current as high as 8 mA with a large active diameter of 24 μm for easy optical alignment. Furthermore, the nonlinear driving of a wavelength sweeping laser in the self-heterodyne beating setup can generate an optical pulse train like waveform, providing an effective optical modulation depth of up to 158%, which leads to a maximum photo-generated RF power (at 10 GHz) from our APD be as high as +5.5 dBm. Futhermore, in order to fulfill the bandwidth requirement for next generation ethernet systems, we require 100G APDs. We demonstrated a novel vertical-illuminated avalanche photodiode (APD) with a In0.52Al0.48As multiplication (M-) layer. The cascaded M-layer design combined with the unique p-side up mesa structure allows relaxation of the fundamental trade-off between the gain-bandwidth product and the dark current. This leads to the simultaneous high-responsivity, high-speed, high-saturation-power, and low-dark current characteristics of our APDs. At around 0.9 Vbr operation, the demonstrated device with its simple top-illuminated structure and large active window (mesa) diameter of 14 (24) μm exhibits a high responsivity (2.23 A/W), wide optical-to-electrical bandwidth (30 GHz), large gain-bandwidth product (270 GHz), low dark current (~200 nA), and a saturation current as high as 11 mA. In order to further improve Gain Bandwidth Product (GBP), flip-chip bonding APDs with 14μm window diameters are demonstrated having wide-bandwidth (36GHz), high-responsivity (3.4A/W), low dark current (175nA) and high MMW output power (-1dBm at 40GHz) can be achieved simultaneously with 12.5mA Isat under 0.9Vbr. The excellent performance of this APDs structure opens up new possibilities to further enhance the sensitivity performance of receivers for coherent communications or 106 Gbit/sec PAM-4 applications. |
