我們提出具高傳輸(大於25 Gbit/sec)、高響應度、高線性度、高增益頻寬積且低暗電流表現的正面收光且藉由蝕刻出圓柱的In0.52Al0.48As累增崩潰光二極體。為了避免元件表面崩潰和繁瑣的保護環結構(Guard ring structure)，此元件磊晶結構主要是N型摻雜在磊晶片的下方，且由In0.52Al0.48As組成的累增(Multiplication)層則設計靠近N型摻雜並在整個磊晶結構的下方。 此外，我們設計元件結構用兩個圓柱裡面包含兩層電荷(Charge)層，以此方式去把累增層裡的電場強烈得局限在中心並減少圓柱周圍的崩潰機會。與背面收光和成本較高的覆晶封裝技術(flip-chip bond)相比，我們提出的元件有簡單的正面收光結構、有較大的25 m主動區半徑能更輕易地去做光學上的對光、可以在單位增益下(unit gain)達到合理的擊穿響應度(0.53 A/W使用1.31 m的波長量測)和在低增益(MG= ~ 6.3)下操作可以擁有良好的3-dB頻率響應(17.5 GHz)、高增益頻寬積(410GHz且在單位增益下擁有55%的外部量子效率)且在高功率（1 mW）和0.9 Vbr操作下保持不變的頻率響應（17.5 GHz），此增益頻寬積(235GHz-A/W)甚至比日本NTT(214GHz-A/W)使用覆晶封裝的值更大。經由將APD封裝在25 Gbit / sec轉阻放大器（TIA）規格中並應用於100 Gbit / sec 接收器光學子組件(ROSA)，在25.78 Gbit / sec傳輸量下擁有約-20 dBm光調製幅度（OMA）的良好靈敏度。這樣的表現已經可以滿足100 GbE-ER-4 lite（40 km）系統所需的接收器靈敏度（-18.5 dBm OMA）。 ;A novel type of top-illuminated, etch-mesa In0.52Al0.48As-based avalanche photodiode (APD) with high-speed, high responsivity, high linearity, high Gain-Bandwidth product and low dark current performance has been demonstrated. The 25G APD device is composed of n-side down design with the In0.52Al0.48As multiplication (M) layer buried at the bottom to avoid the issues of surface breakdown and complex guard ring structure. In addition, we demonstrate that the new structure with two charge layers and daul mesas can effectively confine the electric-field within the center of M-layer and minimize the edge breakdown around the periphery of mesa. In contrast to the costly flip-chip bonding package with backside illumination, our demonstrated device is based on a simple top-illuminated structure that includes a large active diameter of 25m for easy optical alignment, a reasonable punch-through responsivity (0.53 A/W at 1.31 m wavelength), and a good 3-dB optical-to-electrical bandwidth (17.5GHz) under low gain operations (MG≒6.3) and large gain-bandwidth product (GBP) (410 GHz; 55% external efficiency at the unit gain) while maintaining invariant high-speed (17.5 GHz) under high-power (1 mW) and 0.9 Vbr operations, this GBP value (235 GHz-A/W) is even larger than NTT’s achievement (214 GHz-A/W) by using the flip chip packages. By packaging the demonstrated APD with a 25 Gbit/sec trans-impedance amplifier in a 100 Gbit/sec ROSA package, a good sensitivity of around -20 dBm optical modulation amplitude (OMA) at 25.78 Gbit/sec data rate. Such performance can meet the required receiver sensitivity (-18.5 dBm OMA) in 100 GbE-ER-4 lite (40 km) system.
