GeSn-Based Multiple-Quantum-Well Photodetectors for Mid-Infrared Sensing Applications

Silicon (Si)-based mid-infrared (MIR) photonics has promising potential for realizing next-generation ultra-compact spectroscopic systems for various applications such as label-free and damage-free gas sensing, medical diagnosis, and defense. The epitaxial growth ofGe₁₋ₓ Snₓalloy on Si substrate provides the promising technique to extend the cut-off wavelength of Si photonics to MIR range by Sn alloying. Here, we present the theory and simulation of heterojunctionp-i-nMIR photodetectors (PDs) withGe0.87 Sn0.13/ Ge0.92 Sn0.08quantum-wells with an additional Ge0.91Sn0.09layer to elongate the photoabsorption path in the MIR spectrum. The incorporation of QW pairs (N) enables the light-matter interaction due to the carrier and optical confinement in the active region. As a result, the spectral response of the device is enhanced in the MIR range. Devices with varying N were compared in terms of various figure-of merits including dark-current, a photocurrent-to-dark current ratio, detectivity, spectral responsivity, and noise equivalent power (NEP). Additionally, parasitic capacitance-dependentRCand 3dB bandwidth were also studied using a small-signal equivalent circuit model. The proposed device exhibited the extended photodetection wavelength at~ 3370\,nmandIₚₕ /. Idarkup to~ 7.3× 10³with a dark current of~ 56.3\,nAforN=8at 300 K. At a bias of −3V, the proposed device achieved the spectral responsivity of 0.86 A/W at 2870 nm and 0.55 A/W at 3300 nm, detectivity more than2.5× 10⁹Jones and a NEP less than2.1× 10⁻¹³\,W Hz-0.5forN=8at 3250 nm. The calculated 3dB bandwidth of 47.8 GHz, the signal-to-noise ratio (SNR), and linear dynamic range (LDR) of 93 dB and 74 dB were achieved at 3300 nm forN=8. Thus, these results indicate that the proposed GeSn-based QWp-i-nPDs pave the pathway towards the realization of new and high-performance detectors for sensing in the MIR regime.