| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 98 === 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.
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