Investigation of the Effect of Quantum Well Doping on QWIP Operating Temperature

Introduction. Quantum well infrared photodetectors (QWIPs) are among the key components of modern infrared imaging systems and are widely used for various applications, including space research, medical diagnostics, etc. One of the most important characteristics of a QWIP is the background-limited performance (BLIP) temperature, which is determined based on the equality condition between the background current and the dark current flowing through the photodetector. This parameter represents the operating temperature of the photodetector. Increasing the operating temperature can significantly reduce the requirements imposed on the cooling system. Since the background current depends on environmental conditions and the cryostat aperture, it is primarily requir ed to reduce the dark current values. The dark current is strongly dependent on the doping level of the quantum wells. However, the doping concentration also affects the photodetector sensitivity, creating a trade-off between sensitivity and dark current level.
Aim. To investigate the effect of the doping level of quantum wells based on the GaAs/AlGaAs material system on the BLIP temperature.
Materials and methods. Experimental photodetectors were fabricated by molecular beam epitaxy. The parameters of the samples were selected to ensure a peak spectral response wavelength in the range of 8…9 μm. The variable parameter was the doping level of the quantum wells with silicon. After completing the planar processing technological route, the current–voltage characteristics of all test photodetectors were measured in the temperature range of 65…77 K, and the corresponding curves of static current sensitivity were plotted.
Results. A reduction in the doping level from 9.0·1017 to 4.5·1017 cm–3 was found to lead to a significant decrease in the dark current within the operating voltage range. This made it possible to increase the BLIP temperature from 69 to 71 K. This was associated with the expected decrease in photosensitivity; however, its value remained above the threshold level of 0.15 A/W.
Conclusion. The obtained data demonstrate that optimization of the quantum well doping level in QWIPs provides for a reduction in the photodetector dark current. As a result, the device can be operated at higher temperatures.

1. Mid-Infrared Semiconductor Optoelectronics. Ed. by Krier A. London, Springer, 2007, 752 p. doi: 10.1007/1-84628-209-8

2. Ivanov R., Högnadóttir S., Ramos D., Evans D., Visser D., Rihtnesberg D., Smuk A., Becanovic S., Sehlin S., Almqvist S., Smuk S., Höglund L., Costard E. QWIP: Still the Best Solution for High-End Applications in LWIR. Infrared Technology and Applications XLIX. Proc. of SPIE. 2023, vol. 12534, pp. 356–364.

3. Gunapala S. D., Bandara S. V., Liu J. K., Luong E. M., Rafol S. B., Mumolo J. M., Ting D. Z., Bock J. J., Ressler M. E., Werner M. W., LeVan P. D., Chehayeb R., Kukkonen A., Levy M., LeVan P., Fauci M. A. Quantum Well Infrared Photodetector Research and Development at Jet Propulsion Laboratory. Infrared Physics & Technology. 2001, vol. 42, iss. 3–5, pp. 267–282. doi: 10.1016/S1350-4495(01)00085-8

4. Choi K.-K., Lin C.-H., Leung K.-M., Tamir T. QWIP Structural Optimization. Materials for Infrared Detectors II. Proc. of SPIE. 2002, vol. 4795, pp. 27–38. doi: 10.1117/12.453827

5. Berurier A., Nedelcu A. Optimization of Light Polarization Sensitivity in QWIP Detectors. Infrared Physics & Technology. 2013, vol. 59, pp. 118–124. doi: 10.1016/j.infrared.2012.12.025

6. Lu H., Li N., Zhou X., Li Zh., Chen P., Xu J., Li X., Lu W. An LWIR QWIP FPA with Sub-5mK NETD and Large Dynamic Range. Infrared Physics & Technology. 2025, vol. 144, art. no. 105629. doi: 10.1016/j.infrared.2024.105629

7. Das M. K., Lal R. K. Modeling of Quantum Well Infrared Photo Detector for Long Wavelength Infrared Detection. IETE J. of Research. 2017, vol. 63, iss. 5, pp. 719–727. doi: 10.1080/03772063.2017.1313138

8. Smuk S., Gromov A., Alverbro J., Merken P., Souverijns T., Haga D., Malm H., Asplund C., Borglind J., Becanovic S., Tinghag P., Martijn H., Hirschauer B. Optimisation of QWIP Detectors for Space Applications. Sensors, Systems, and Next-Generation Satellites IX. Proc. of SPIE. 2005, vol. 5978, pp. 397–406. doi: 10.1117/12.632799

9. Etteh N. E. I., Harrison P. Quantum Mechanical Scattering Investigation of the Dark Current in Quantum Well Infrared Photodetectors (QWIPs). Infrared Physics & Technology. 2003, vol. 44, iss. 5–6, pp. 473–480. doi: 10.1016/S1350-4495(03)00169-5

10. Downs C., Vandervelde T. E. Progress in Infrared Photodetectors Since 2000. Sensors. 2013, vol. 13, iss. 4, pp. 5054–5098. doi: 10.3390/s130405054

11. Bhan R. K., Dhar V. Recent Infrared Detector Technologies, Applications, Trends and Development of HgCdTe Based Cooled Infrared Focal Plane Arrays and Their Characterization. Opto-Electronics Review. 2019, vol. 27, no. 2, pp. 174–193. doi: 10.1016/j.opelre.2019.04.004

12. Schneider H., Liu H. C. Quantum Well Infrared Photodetectors: Physics and Applications. Berlin, Heidelberg, Springer, 2007, 248 p. doi: 10.1007/978-3-540-36324-8

13. Bogoslovskaya L. S., Dudin A. L., Zubkov V. I. Influence of Barrier Width on QWIP Operating Voltage. J. of the Russian Universities. Radioelectronics. 2024, vol. 27, no. 4, pp. 72–80. doi: 10.32603/1993-8985-2024-27-4-72-80

14. Schneider H., Koidl P., Walther M., Fleißner J., Ziegler J. GaAs/AIGaAs Quantenfilm Photodetektoren für Kameras im 8...12µm-Bereich. tm-Technisches Messen. 1999, vol. 66, no. 9, pp. 344–349.

15. Billaha A., Das M. K. Influence of Doping on the Performance of GaAs/AlGaAs QWIP for Long Wavelength Applications. Opto-Electronics Review. 2016, vol. 24, no. 1, pp. 25–33. doi: 10.1515/oere-2016-0006

16. Nutku F., Erol A., Gunes M., Buklu L. B., Ergun Y., Arikan M. C. I–V Characterization of a Quantum Well Infrared Photodetector with Stepped and Graded Barriers. Superlattices and Microstructures. 2012, vol. 52, no. 3, pp. 585–593. doi: 10.1016/j.spmi.2012.06.010

17. Yang Y., Liu H. C., Shen W. Z., Li N., Lu W., Wasilewski Z. R. Optimal Doping Density for Quantum-Well Infrared Photodetector Performance. IEEE J. of Quantum Electronics. 2009, vol. 45, no. 6, pp. 623–628. doi: 10.1109/JQE.2009.2013119

18. Dudin A. L., Katsavets N. I., Krasovitsky D. M., Filaretov A. G., Chaly V. P. Standardization of Manufacturing Technologies for Matrices for Cooled Thermal Imagers: "Hot" or "Cold"? Electronics: Science, Technology, Business. 2022, no. 2, pp. 114–119. doi: 10.22184/1992-4178.2022.213.2.114.119