Mid-infrared GaSb-based resonant tunneling diode photodetectors for gas sensing applications

We present resonant tunneling diode-photodetectors (RTD-PDs) with GaAs_0.15Sb_0.85/AlAs_0.1Sb_0.9 double barrier structures combined with an additional quaternary Ga_0.64In_0.36As_0.33Sb_0.67 absorption layer covering the fingerprint absorption lines of various gases in the mid-infrared wavelength spectral region. The absorption layer cut-off wavelength is determined to be 3.5 µm and the RTD-PDs show peak-to-valley current ratios up to 4.3 with peak current densities of 12 A/cm^-2.The incorporation of the quaternary absorption layer enables the RTD-PD to be sensitive to illumination with light up to the absorption lines of HCl at 3395 nm. At this wavelength, the detector shows a responsivity of 6.3 mA/W. At the absorption lines of CO₂ and CO at 2004 nm and 2330 nm respectively, the RTD-PD reaches responsivities up to 0.97 A/W. Thus RTD-PDs pave the way towards high sensitive mid-infrared detectors that can be utilized in tunable laser absorption spectroscopy.