High-Performance Normal-Incidence Ge/Si Meta-Structure Avalanche Photodetector

Abstract

A high-speed and high-sensitivity avalanche photodetector (APD) is a critical component of a high-data-rate and low-power optical-communication link. In this paper, we study a high-speed and high-efficiency Ge/Si heterostructure APD. First, we numerically study the speed performance of the APD by analyzing frequency response. An optimized epitaxial structure of the high-speed APD is designed. In the absence of RC time effects, the APD exhibits a fast pulse response (full-width at half-maximum) of 10 ps and a high 3 dB bandwidth of 33 GHz at a high-gain value of 10. Taking device size and the corresponding RC time effects into account, the APD still achieves a high 3 dB bandwidth of 29 GHz at a gain value of 10. Moreover, a novel subwavelength periodic hole array is designed on the normal-incidence APD for enhancing light absorption without sacrificing speed performance. Near-perfect absorption is almost achieved by an infinite-period hole array due to the coupling of dual-resonance modes. A high-absorption efficiency of 64% is obtained by a limited-sized hole array in the high-speed APD. This work provides a promising method to design high-speed and high-efficiency normal-incidence Ge/Si heterostructure APDs for optical interconnect systems.