GeSn QD decorated graphene/n-Ge mixed-dimensional heterostructure for extended shortwave infrared detection

We report an all-group-IV photodiode enabling extended shortwave infrared detection by integrating sputtered Ge_0.84Sn_0.16 quantum dots (QDs) on a graphene (Gr)/n-Ge substrate via quasi-van der Waals epitaxy. The Fermi level depinning of n-Ge by Gr and work function modulation of Gr by GeSn QDs enhance the Schottky barrier height between GeSn-QDs decorated Gr and n-Ge to 0.49 eV, thus suppressing the dark current. The GeSn QDs facilitate the extension of the detection range up to 2400 nm and naturally act as hole trapping centers producing photocurrent gain. Consequently, high responsivities of 2.4/1.8 A/W at 1310/1550 nm with corresponding detectivities of 1.4 × 10¹⁰/1.1 × 10¹⁰ Jones alongside a fast response time of <60 µs were achieved. This approach presents a robust, cost-effective solution for extending the spectral range of Si-based photonics.