我們提出一個新的平面型InAlAs分離式吸收、傳輸、電荷、累增之累增崩潰光二極體(SATCM APD)結構。在傳統的分離式吸收、電荷、累增之累增崩潰光二極體(SACM APD)結構中插入了一層InP傳輸層，藉此我們可以在0.9Vbr的操作下觀察到一3-dB頻寬增強現象，且可以降低RC頻寬限制和二次電洞傳輸時間兩者之間的利弊關係。因此，我們可以將我們提出的SATCM APD的主動區的直從典型的10Gbit/sec APD 的30?m 增加到40?m或50?m而仍然能維持在10Gbit/sec的高速操作。 除此之外，由於我們的SATCM APD 結構中的厚空乏區(~2.5?m)和適當的電荷層摻雜濃度，我們可以在達到擊穿電壓(~18V)時，就擁有接近2的增益，在元件發生崩潰之前，有接近20伏的操作電壓範圍。使用我們提出的SACTM APD 結構，在主動區直徑為40?m or 50?m時，可以成功達到在0.9Vbr (~39V) 操作下，有頻寬增強的現象和可接受的低暗電流(~50nA)；而在10Gbit/sec 操作時，有-23dBm的靈敏度。We demonstrate a novel type of planar InAlAs based separated absorption, transport, charge, and multiplication (SATCM), avalanche photodiode (APD) structure. By inserting an additional InP transport layer in the traditional InAlAs based SACM-APD structure, a strong 3-dB bandwidth enhancement (BE) phenomenon under 0.9 breakdown voltage (0.9Vbr) operation has been observed, which greatly releases the trade-off between RC-limited bandwidth and secondary-hole transport time. Through the use of such phenomenon, we can thus increase the active diameter of our SATCM-APD from 30?m, which is the typical size of 10Gbit/sec APD, to around 50 or 40?m and sustain its capability for 10Gbit/sec high-speed operation with a great improvement in alignment tolerance. Furthermore, due to a thick depletion layer (~2.5?m) in our SATCM-APD structure, by properly optimizing the charge layer doping density, we can achieve a multiplication gain around 2 at punch-through voltage (~18V) with a 20V operation voltage window till breakdown occurs. Under 0.9Vbr (~39V) operation with BE phenomenon, a reasonable dark current (~50nA) and sensitivity (-23dBm) at 10Gbit/sec operation by use of our SATCM-APD with a 40 or 50?m active diameter has been successfully achieved.
