Among the available detectors, semiconductor photodetectors operating at short wavelength infrared spectrum, or SWIR, have attracted significant attention of researchers due to their excellent optical and electrical properties that enable them to meet various demands in remote sensing. However, these devices are susceptible to high dark current induced by the minority carrier diffusion. To this note, UCLA and Cardiff University researchers investigated the feasibility of suppressing minority carrier diffusion by integrating small bandgap photoabsorber on large bandgap substrates. In the study, they prepared InAs nanowire photodiodes constituting of nanostructured photoabsorbers on InP substrates with p-n heterojunctions. The nanowires were grown by selective-area metal-organic chemical vapor deposition (SA-MOCVD). They further characterized diode performance and observed room-temperature spectral response at SWIR. The results showed that nanowire-substrate heterojunctions can lead the same dark current density as commercial SWIR detectors. Their research work was recently published in Nano Letters and Nanoscale.
“Currently, rapid growth in nanotechnology has enabled the development of various nanomaterials to tackle different challenges. Likewise, nanowires with excellent properties i.e., heteroepitaxy and small junction area, serve as strong candidates in delivering high-quality materials and novel device structures. Thus, it is very promising to implement such nanoscale materials into optical devices for photodetection with high efficiency,” says Dr. Dingkun Ren, the lead author from UCLA in a statement to Advances in Engineering.
To validate their study, the team compared the obtained dark current density from nanowire devices to that from the best commercial InAs p-i-n diodes. “We benchmarked our nanowire devices against currently available detectors on market,” says Ren, “Our dark current density, which is normalized to the junction area, is at the same level of those detectors. Our devices also show desirable diode performance at room temperature with rectification higher than 300.” The team further investigated the impact of nanowire surface non-radiative recombination on dark current. “We believe the current can be reduced by at least one more order with proper surface passivation,” says Ren.
This research perfectly meets the increasing demands and critical requirements of the optical sensing industry. It enables the fundamental understanding of the dark current in nanostructured semiconductor materials and paves the way for future integration of nanostructured photoabsorbers to enhance detection performance at SWIR regime.
Ren, D., Meng, X., Rong, Z., Cao, M., Farrell, A. C., & Somasundaram, S. et al. (2018). Uncooled Photodetector at Short-Wavelength Infrared Using InAs Nanowire Photoabsorbers on InP with p–n Heterojunctions. Nano Letters, 18(12), 7901-7908.Go To Nano Letters
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