Rapid technological advancements optics has led to the development III-V semiconductor photodetectors with important applications in remote sensing. In particular, photodetectors operating at midwave-length infrared (MWIR, 3µm-5µm) region have attracted significant attention of researchers. Based on their operation requirements, cooling accessories are always necessary to enhance the sensitivity. Consequently, considering the growing complexity of these photodetectors, developing uncooled photodetectors with high-resolution and high sensitivity at MWIR is highly desirable.
To enhance room-temperature photodetection at MWIR, one solution is to develop nanowire-based detectors. The enabling physics is that the material volume of nanowires is very small and thus the thermal noise at room temperature can be significantly reduced. However, achieving photodetection beyond 3µm wavelength remains difficult. This can be attributed to large surface-to-volume ratio of nanowire structures–the noise from surface, i.e., surface leakage, is a dominant factor. Thus, it is critical to develop a surface passivation technique to reduce the leakage for achieving higher quantum efficiency.
In a recent research paper published in Nano Letters, Dr. Dingkun Ren and colleagues from University of California at Los Angeles and Cardiff University demonstrated room-temperature InAsSb nanowire photodetectors at 3.4µm wavelength. The nanowires were grown by a technique called selective-area metal-organic chemical vapor deposition (SA-MOCVD). Importantly, they developed dielectric Al2O3 layers to conformally passivate InAsSb nanowire surfaces. Using this technique, they achieved room-temperature photoluminescence emission from InAsSb nanowire arrays, which covers the entire MWIR regime from 3µm to 5µm. “A common passivation technique is to grow a layer of large bandgap III-V material to coat nanowires in the growth chamber. However, it is very difficult and challenging to find a proper material lattice-matched with InAsSb. Moreover, it is very hard to tune the growth conditions,” Ren comments. Additionally, the team developed an associated device fabrication process to expose nanowire tips for metal contacts while preserving nanowire sidewall passivation.
This achievement is based on their accumulated knowledge on III-V nanowire optoelectronics, including heteroepitaxy of InAs-based nanowires on InP substrates, carrier dynamics in nanowires, and nanowire surface recombination. “We are very excited to observe photodetection at 3.4µm at room temperature. We believe that our study will pave the way for the continued advancement of InAsSb nanowire photodetectors at MWIR region,” says Ren.
Ren, D., Azizur-Rahman, K., Rong, Z., Juang, B., Somasundaram, S., & Shahili, M. et al. (2019). Room-Temperature Midwavelength Infrared InAsSb Nanowire Photodetector Arrays with Al2O3 Passivation. Nano Letters, 19(5), 2793-2802.Go To Nano Letters
Ren, D., Scofield, A. C., Farrell, A. C., Rong, Z., Haddad, M. A., Laghumavarapu, R. B. et al. (2018). Exploring Time-Resolved Photoluminance for Nanowires Using a Three-Dimensional Transient Model. Nanoscale, 10(16), 7792-7802.Go To Nanoscale
Ren, D., Farrell, A., Williams, B. S. & Huffaker D. L. (2017). Seeding Layer Assisted Selective-Area Growth of As-Rich InAsP Nanowires on InP Substrates. Nanoscale, 9(24), 8220-8228.Go To Nanoscale