Periodic Reporting for period 1 - ECOSWIR (Short-wave infrared photodetectors based on low-cost, environmentally friendly InSb colloidal quantum dots)
Reporting period: 2022-09-01 to 2024-08-31
The development of low-cost optoelectronic devices in the visible and near infrared (NIR), such as digital image sensors and solid-state lighting, and their introduction into the consumer electronics market, has drastically changed the way we live and communicate today. Access to longer wavelengths into the short-wave infrared (SWIR, 1-2 um), would open up a huge number of applications, such as hyperspectral, 3D and adverse weather imaging, night vision for surveillance and automotive safety, spectroscopy for food quality inspection, process/agriculture monitoring, chemical hazard detection, environmental sensing, and biomedical diagnostics etc. leading to a direct and huge impact on quality of life, health, and security, provided that such technologies are available at low cost and high volumes, to serve consumer electronics markets. To address this large consumer market volume the necessity for low-cost, non-toxic, and complementary metal oxide semiconductor (CMOS) compatible SWIR photodetectors is therefore indispensable. To date, the SWIR has been served by costly epitaxial III-V semiconductors, which are not monolithically integrated to silicon (CMOS) electronics, and suffer from high growth cost and low volume manufacturing. Compared to epitaxial technology, solution-processed technology based on colloidal quantum dots (CQDs) is more promising for SWIR photodetectors due to low cost and high-volume manufacturing, and their CMOS integrability. Nowadays, the most mature solution processed CQD SWIR photodetectors are based on lead sulfide (PbS) CQDs. However, these CQDs SWIR photodetectors are facing huge challenges from legislation in the European Union (EU) such as RoHS (“Restriction of Hazardous Substances”), which hinders its further commercial applications. On the other hand, InSb is an environmentally friendly III–V semiconductor which possesses a narrow direct band gap (0.17 eV) and the highest room temperature carrier mobility (7.7 × 104 cm2/V·s) and the smallest exciton binding energy (0.5 meV) of all semiconductors, thus being ideal for SWIR photodetectors. For that reason, ECOSWIR aims to develop a whole new material platform based on non-epitaxial InSb CQDs that, in contrast to current III-V technologies, will enable CMOS compatibility and large-scale production of optoelectronic materials. Utilizing this achievement, ECOSWIR will provide a proof of principle of InSb CQDs SWIR photodetectors with performance that cannot be met by any prior CQDs devices, that will be competitive to the costly epitaxial technology and warrant introduction into high-volume, consumer electronics markets and pave the way towards printable SWIR photodetectors.
As mentioned above, ECOSWIR will have significant impacts in the fields of science, economy and society. More specifically, this proposal aims to develop the first InSb CQDs-based devices covering the whole chain from material synthesis to device fabrication, offering new scientific knowledge, such as, new synthetic scheme for large-scale synthesis of InSb CQDs, new surface passivation for high carrier mobility, and optimized device architectures. Advancing the optoelectronic properties of infrared III-V CQDs for photodetectors will also have implications towards the development of light emitters (LEDs and lasers). The InSb CQDs photodetector proposed by ECOSWIR will enable a new photodetector platform with lower manufacturing cost, improved performance, and RoHS compliance, suited to the needs of volume markets with direct societal and economic benefits. For instance, eye-safe SWIR imaging in the automotive allows cars with night vision and imaging in adverse weather conditions, leading to reduction in car accidents. In addition, low-cost SWIR will bring SWIR lab-spectroscopy systems to consumers for allergen detection/food quality inspection, personalized diagnostics and health/fitness monitoring on wearable devices. Large consumer and automotive manufacturers (e.g. Samsung, VW) are aligned with semiconductor foundries (AMS, ST) on the need for low-cost RoHS compliant infrared sensors, warrantying the industrial relevance of ECOSWIR.
As mentioned above, ECOSWIR will have significant impacts in the fields of science, economy and society. More specifically, this proposal aims to develop the first InSb CQDs-based devices covering the whole chain from material synthesis to device fabrication, offering new scientific knowledge, such as, new synthetic scheme for large-scale synthesis of InSb CQDs, new surface passivation for high carrier mobility, and optimized device architectures. Advancing the optoelectronic properties of infrared III-V CQDs for photodetectors will also have implications towards the development of light emitters (LEDs and lasers). The InSb CQDs photodetector proposed by ECOSWIR will enable a new photodetector platform with lower manufacturing cost, improved performance, and RoHS compliance, suited to the needs of volume markets with direct societal and economic benefits. For instance, eye-safe SWIR imaging in the automotive allows cars with night vision and imaging in adverse weather conditions, leading to reduction in car accidents. In addition, low-cost SWIR will bring SWIR lab-spectroscopy systems to consumers for allergen detection/food quality inspection, personalized diagnostics and health/fitness monitoring on wearable devices. Large consumer and automotive manufacturers (e.g. Samsung, VW) are aligned with semiconductor foundries (AMS, ST) on the need for low-cost RoHS compliant infrared sensors, warrantying the industrial relevance of ECOSWIR.
(i). Developed a synthetic method for producing size-tunable InSb CQDs with distinct first excitonic peaks spanning a wide range from 900 to 1750 nm.
(ii). Achieved the surface trap states passivation of InSb CQDs by growing the InP shell and significantly enhanced the PL intensity of the InSb CQDs with a record PLQY of 4% at 1300 nm.
(iii). Fabricated the InSb CQD SWIR photodetector, which demonstrates competitive features, including a wide linear dynamic range exceeding 128 dB, a maximum EQE of 25% at 1240 nm (and 12% at 1420 nm), a fast photoresponse time of 70 ns, and a specific detectivity of up to 4.4 × 1011 jones.
(ii). Achieved the surface trap states passivation of InSb CQDs by growing the InP shell and significantly enhanced the PL intensity of the InSb CQDs with a record PLQY of 4% at 1300 nm.
(iii). Fabricated the InSb CQD SWIR photodetector, which demonstrates competitive features, including a wide linear dynamic range exceeding 128 dB, a maximum EQE of 25% at 1240 nm (and 12% at 1420 nm), a fast photoresponse time of 70 ns, and a specific detectivity of up to 4.4 × 1011 jones.
In this project, we have developed a synthesis of InSb CQDs that offers wide spectral tunability, high quality of CQDs expressed in adequate size uniformity, simplicity and use of commercially available precursors, and high product yield and well-passivated surface detects, features that are essential for use in optoelectronic device developments. Leveraging these high-quality materials, we demonstrated the first solution-processed InSb CQD SWIR photodetector, with figures of merit that can enable high-frame-rate light sensors for machine vision, gated imaging, and 3D sensing applications. These results not only highlight the tremendous potential of InSb CQDs as a heavy-metal-free active material for SWIR photodetectors but also provide a possible avenue for further advances in colloidal InSb using wet chemistry techniques toward the development of high-performance optoelectronic