我們提出具高傳輸(大於25 Gbit/sec)、高速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型參雜在磊晶片的下方，且由In0.52Al0.48As組成的累增(Multiplication)層則設計靠近N型參雜並在整個磊晶結構的下方。 此外，我們設計元件結構用三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30 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(0.7 A/W使用1.31 m的波長量測)和在低增益(MG= ~ 3)下操作可以擁有良好的3-dB頻率響應(22.5 GHz)。除此之外，我們提出的元件在1.31 m的波長下操作時，可以在中度增益(MG = ~ 5)下承受廣範圍光功率(-17到+4.6 dBm)的變化並同時擁有15 GHz的3-dB 頻率響應。元件在1.55 m的波長下做28 Gbit/sec 傳輸時，有良好的靈敏度(-16 dBm)。 ;A novel type of top-illuminated, etch-mesa In0.52Al0.48As-based avalanche photodiode (APD) with high-speed (>25 Gbit/sec), 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 triple 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 30m for easy optical alignment, a reasonable punch-through responsivity (0.7 A/W at 1.31 m wavelength), and a good 3-dB optical-to-electrical (O-E) bandwidth (22.5 GHz) under low gain operations (MG= ~3). Furthermore, it can sustain the 3-dB bandwidth of 15 GHz over a wide range of launched optical power (-17 to +4.6 dBm) under a moderate gain (MG= ~5) operation at 1.31 m wavelength. High-sensitivity (-16 dBm) for error-free 28 Gbit/sec operation can also be achieved at 1.55 m wavelength.
