# Trends in Performance Limits of the HOT Infrared Photodetectors
## 4 Interband Quantum Cascade Infrared Photodetectors (IB QCIPs)
In MWIR the performance of bPAs devices is higher than commercially available uncooled HgCdTe photodiodes, while in LWIR, the detectivity, D\({}^{*}\) of the TMD photodetectors is the best. The HgCdTe and IB QCIPs response time at 300 K, typically in the order of nanoseconds, is significantly shorter than for 2D material photodetectors. Figure 12 gathers the highest detectivity, D\({}^{*}\) values published in literature for different types of single element photodetectors operating at room temperature. This fact should be clearly emphasized since detectivity, D\({}^{*}\) data marked for commercial photodetectors is typical for pixels of IR FPAs. Figure 12 also presents the fundamental indicator for future trend in development of HOT IR photodetectors. At present stage of HgCdTe technology, the semiempirical Rule 07 is found not to fulfil primary expectations. It is shown that the detectivity, D\({}^{*}\) of low-doping P-i-N HgCdTe (5 \(\times\) 10\({}^{13}\) cm\({}^{-3}\)) photodiodes, operating at 300 K in spectral band above 3 \(\upmu\)m, is limited by background radiation (with detectivity, D\({}^{*}\) level above 10\({}^{10}\) Jones, not limited by detector itself) and can be improved more than one order of magnitude in comparison with predicted by Rule 07. Between different material systems used in fabrication of HOT LWIR photodetectors, only HgCdTe can fulfill required expectations: low doping concentration--10\({}^{13}\) cm\({}^{-3}\) and high SRH carrier lifetime above 1 ms. In this context, 2D material photodetectors and CQD photodetectors cannot compete with HgCdTe photodiodes. The above assessments provide further inspiration for reaching low-cost and high performance MWIR and LWIR HgCdTe FPAs operating in HOT conditions. The performance of T2 SL IB QCIPs is close to HgCdTe photodiodes  
Figure 10: Room-temperature spectral detectivity curves of the commercially available photodetectors [PV Si and InGaAs, PC PbS and PbSe, HgCdTe photodiodes (solid lines reference [33])]. The spectral detectivity curves of new emerging T2 SL IB QCIPs are marked by dashed lines (reference 38). Also the experimental data for different types of 2D material photodetectors are included. Experimental data is taken from [43; 44; 45; 46; 47; 48]. PC—Photoconductor, PV—Photodiode. and quantum cascade photodetectors can operate in temperature > 300 K; however, their disadvantage is a challenging technology and higher fabrication cost. Figure 11: HgCdTe photodiodes, T2 SLs InAs/GaSb IB QCIPs and representative 2D material photodetectors peak detectivity, D\({}^{\ast}\) comparison for 300 K. The measured data for HgCdTe photodiodes according to the VIGO System catalogue [33]. Data for IB QCIPs extracted from selected papers [38]. Data for selected 2D materials is taken from [33; 38; 43; 46; 47; 48]. Figure 12: Detectivity, D\({}^{\ast}\) versus wavelength for the commercially available room-temperature IR photodetectors (PV Si and Ge, PV InGaAs, PC PbS and PbSe, PV HgCdTe). There is also included experimental data for IB QCIP T2 SLs, different type of 2D material and CQD photodetectors taken from literature as marked. The theoretical curves are calculated for the P:i-N HOT HgCdTe devices assuming \(\tau_{\rm{SRH}}\) = 1 ms, the absorber doping 5 \(\times\) 10\({}^{13}\) cm\({}^{-3}\) and the active region thickness t = 5 \(\upmu\)m. Experimental data is taken from [13; 33; 34; 38; 43; 46; 47; 48; 49; 50; 51]. PC—Photoconductor, PV—Photodiode.