A Simulation-Based Study of Back-Illuminated Lateral Ge/GeSn/Ge Photodetectors on Si Platform for Mid-Infrared Image Sensing

Abstract

GeSn/Ge heterojunction photodetectors (PDs) have great potential to outperform conventional mid-infrared (MIR) sensors. In this work, simulated analysis is performed to demonstrate the back-illuminated lateral double <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{Ge/}{\text{Ge}}_{\text{0.90}}{\text{Sn}}_{\text{0.10}}\text{/Ge}$</tex-math> </inline-formula> heterojunctions p-i-n PDs for MIR imaging. This lateral PDs configuration is compatible with current complementary metal–oxide–semiconductor (CMOS) technology, yielding reduced fabrication complexity and offering high resonance in optical characteristics (between 2000-and 2700-nm wavelength range), viable for high-performance operation in MIR wavelength bands. This work also investigates the effects of high-density point dislocation at GeSn/Ge heterointerface on various performance metrics, including dark current, photocurrents, detectivity, and noise-equivalent-power (NEP) of PDs. The results indicate that the defects have less impact on detectivity and NEP and have negligible impact on the collection of photogenerated carriers and thus responsivity. The device shows a maximum 3-dB optoelectrical bandwidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 92.4 GHz, which is among the highest of other GeSn p-i-n PDs. In addition, even in the presence of defects, the device achieves high responsivity in MIR bands and its values are 0.39, 1.45, and 0.25 A/W at the operating wavelengths of 2000, 2310, and 2700 nm, respectively. Thus, the proposed work can be a major step toward GeSn-based PDs on the Si platform for MIR imaging applications.