Low-Cost High-Performance p-GaSe/i-GeSn/n-GOI Heterojunction Photodiode for Visible to Short-Wave Infrared Multispectral Detection

In this work, a low-cost and high-performance p-GaSe/i-GeSn/n-Ge-on-insulator van der Waals (vdW) heterojunction photodetector (PD) is demonstrated with a Sn-composition-graded i-GeSn absorption region. Featuring a sputtering-grown Ge0.848 Sn0.152 top layer, the PD extends its cutoff wavelength beyond 2400 nm, simultaneously boosting its response to visible (VIS) light. This enhancement is achieved through using wide bandgap GaSe flake as the p-type region, resulting in a flat broadband photo-response spectrum from VIS to short-wave infrared (SWIR) bands. Moreover, an ultralow dark current density of 0.55 mA/cm2 is achieved owing to the large bandgap of GaSe and graded barriers within the GeSn layers. The specific detectivity at 2000 nm reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${3.5}\times {10}^{{10}}$ </tex-math></inline-formula> Jones, alongside a rapid response time of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$49.5\mu $ </tex-math></inline-formula>s under −1 V bias at room temperature. These outcomes highlight the potential of the mixed-dimensional GeSn vdW heterojunction PD as a new pathway for low-cost multispectral detection ranging from VIS to SWIR wavelengths.