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 of Ge1-xSnx alloy 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 heterojunction p-i-n MIR photodetectors (PDs) with Ge0.87Sn0.13/Ge0.92Sn0.(08) quantumwells with an additional Geom 5110 . 0g layer to elongate the photoabsorption path in the MIR spectrum. The incorporation of OW 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-dependent RC and 3dB bandwidth were also studied using a small-signal equivalent circuit model. The proposed device exhibited the extended photodetection wavelength at similar to 3370 nm and I-ph/I-dark up to similar to 7.3 x 10(3 )with a dark current of similar to 56.3 nA for N = 8 at 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 NW at 3300 nm, detectivity more than 2.5 x 10(9) Jones and a NEP less than 2.1 x 10(-13) WHz(-0.5 )for N = 8 at 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 for N = 8. Thus, these results indicatethat the proposed GeSn-based OW p-i-n PDs pave the pathway towards the realization of new and high-performance detectors for sensing in the MIR regime.