Simultaneous enhancement of the bandwidth and responsivity in high-speed avalanche photodiodes with an optimized flip-chip bonding package

• Published in: Optics express Vol. 31; no. 16; p. 26463
• Main Authors: Naseem, Chen, Nan-Wei, Parvez, Syed Hasan, Ahmad, Zohauddin, Yang, Sean, Chen, H-S, Chang, Hsiang-Szu, Huang, Jack Jia-Sheng, Shi, Jin-Wei
• Format: Journal Article
• Language: English
• Published: 31.07.2023
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.494510

The enhancement in responsivity of photodiodes (PDs) or avalanche photodiodes (APDs) with the traditional flip-chip bonding package usually comes at the expense of degradation in the optical-to-electrical (O-E) bandwidth due to the increase of parasitic capacitance. In this work, we demonstrate backside-illuminated In 0.52 Al 0.48 As based APDs with novel flip-chip bonding packaging designed to relax this fundamental trade-off. The inductance induced peak in the measured O-E frequency response of these well-designed and well-packaged APDs, which can be observed around its 3-dB bandwidth (∼30 GHz), effectively widens the bandwidth and becomes more pronounced when the active diameter of the APD is aggressively downscaled to as small as 3 µm. With a typical active window diameter of 14 µm, large enough for alignment tolerance and low optical coupling loss, the packaged APD exhibits a moderate damping O-E frequency response with a bandwidth (36 vs. 31 GHz) and responsivity (3.4 vs. 2.3 A/W) superior to those of top-illuminated reference sample under 0.9 V br operation, to attain a high millimeter wave output power (0 dBm at 40 GHz) and output current (12.5 mA at +8.8 dBm optical power). The excellent static and dynamic performance of this design open up new possibilities to further improve the sensitivity at the receiver-end of the next-generation of passive optical network (PON) and coherent communication systems.