Gain-bandwidth-limited response in long-wavelength avalanche photodiodes

Abstract

The gain-bandwidth(GB)-limited response of In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> As/ InP heterostructure avalanche photodiodes (APD's) and related devices used in long-wavelength digital optical receivers is calculated. We find that these diodes, as currently designed, are useful at bit rates <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B \lsim 2</tex> Gbit/s when employed in conjunction with high-sensitivity optical receivers. Response at higher bit rates may be obtained depending on the details of device design. On the other hand, use of poor-quality receivers that require moderate-to-high values of optimum gain can significantly degrade the performance of heterostructure APD's at high bit rates due to GB limitations. We also show that APD receiver bandwidth can be expressed in terms of the sensitivity obtained using the receiver in conjunction with a p-i-n photodiode. It is found that the response speed of optimized receivers is lowest for an APD effective ionization rate ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k = 0.5</tex> .