High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate

TL;DR

This paper presents a high-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiode on SOI substrate, achieving significantly improved absorption efficiency and responsivity for high-speed optical applications.

Contribution

The study introduces a novel vertical-illumination Si/Ge UTC photodiode with enhanced absorption efficiency and responsivity, overcoming previous speed-responsivity trade-offs.

Findings

Maximum absorption efficiency 2.4 times greater than silicon substrate

Responsivity at 1550 nm of 0.18 A/W, 50% higher than previous designs

Device fabrication successfully demonstrated with improved performance

Abstract

Si/Ge uni-traveling carrier photodiodes exhibit higher output current when space-charge effects are overcome and thermal effects are suppressed, which is highly beneficial for increasing the dynamic range of various microwave photonic systems and simplifying high-bit-rate digital receivers in different applications. From the point of view of packaging, detectors with vertical-illumination configuration can be easily handled by pick-and-place tools and are a popular choice for making photo-receiver modules. However, vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from inter-constraint between high speed and high responsivity. Here, we report a high responsivity vertical-illumination Si/Ge UTC photodiode based on a silicon-on-insulator substrate. The maximum absorption efficiency of the devices was 2.4 times greater than the silicon substrate owing to constructive interference. The Si/Ge UTC photodiode was successfully fabricated and had a dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25% thinner Ge absorption layer.