Enhanced Detectivity of Ge 0.854 Sn 0.146 Mid-Infrared Photodiodes by Layer Transfer

Efficient and cost-effective mid-infrared photodetectors that operate at room temperature are essential for a wide range of applications, including environmental monitoring, medical diagnostics, surveillance, and target recognition. A cost-efficient solution to implement such photodetectors is to use GeSn alloys, as they can be grown directly onto 200 and 300 mm germanium-buffered silicon wafers. However, the large lattice mismatch associated with the epitaxial growth of GeSn on Ge compromises the growth of thick, high-quality active layers, thus, limiting the responsivity of GeSn-based photodetectors. Herein, we demonstrate the integration of Ge0.854Sn0.146 heterostructures onto metal layers, yielding a 3-fold enhancement in the room-temperature photodetector responsivity at 2.5 μm, with a cutoff wavelength of 3.1 μm. Transfer on metal does not degrade the optoelectronic properties of absorbing layers. A 3.5-fold enhancement of the room temperature specific detectivity (D* = 6.5 × 108 cm·Hz1/2·W–1) is measured at 2.5 μm relative to that of conventional as-grown control photodetector. This approach enhances the performance of GeSn photodetectors at specific wavelengths for a given thickness of the transferred stack, overcoming the limitations of thin absorbing GeSn layers.