Unraveling the root cause of persistent dark current in TeSe heterojunction: interface metallization under stress

Researchers have uncovered the fundamental mechanism behind persistent dark current in Te-Se alloy-based infrared photodiodes, identifying interface metallization as the culprit. High interface stress between Te_0.6Se_0.4 and ZnO causes Se atoms to diffuse, forming a detrimental Te_0.75Se_0.25 metallic phase that hinders carrier transport. This breakthrough in interface engineering opens new possibilities for high-performance infrared detection technologies across multiple applications.

This study has revealed the root cause of a long-standing issue plaguing tellurium-selenium (Te-Se) alloy-based infrared photodetectors, and demonstrated how interface stress induces unwanted metallization at material boundaries, significantly degrading device performance. More importantly, this study has developed an elegant solution by introducing a thin TeO₂ modification layer that effectively mitigates this problem.

"We've discovered that under high interface stress conditions, selenium atoms migrate from the Te_0.6Se_0.4 layer into the ZnO region, creating a new metallic Te_0.75Se_0.25 phase," explains the lead researcher. "This metallic phase acts as a barrier to carrier transport, resulting in elevated dark current and reduced quantum efficiency—two critical parameters for infrared photodetector performance."

Infrared photodetectors serve as essential components in numerous cutting-edge technologies, from night vision and thermal imaging to medical diagnostics and autonomous vehicles. Te-Se alloys have emerged as promising candidates for next-generation infrared detection due to their tunable bandgap and relatively simple fabrication processes compared to traditional materials like mercury cadmium telluride (HgCdTe).

The team's innovative solution involves inserting a nanometer-thin TeO₂ modification layer between the Te_0.6Se_0.4 and ZnO interface. This strategic addition dramatically reduces interface stress, preventing selenium atom diffusion and subsequent metallization. As a result, the modified devices exhibited dark current reduction by more than two orders of magnitude and quantum efficiency improvement from approximately 30% to 75%.

"What makes this work particularly significant is that it addresses a fundamental materials science challenge through interface engineering," notes the research team. "Rather than abandoning Te-Se alloys or pursuing more complex material systems, we've demonstrated that thoughtful interface design can overcome inherent limitations."

The implications of this research extend beyond Te-Se alloy-based photodetectors. The interface stress mitigation approach provides valuable insights for other semiconductor device systems where lattice mismatch and interface stress pose similar challenges. The findings could influence the development of various optoelectronic devices, including solar cells, light-emitting diodes, and other types of sensors.

Looking ahead, the researchers plan to further optimize the TeO₂ modification layer thickness and deposition process to maximize device performance. They are also exploring the application of similar interface engineering approaches to other material systems with promising infrared detection capabilities.

This research represents a significant step forward in the development of high-performance, cost-effective infrared photodetectors that could enable more widespread deployment of infrared sensing technologies across consumer electronics, healthcare devices, environmental monitoring systems, and security applications.

This work was supported by the National Key Research and Development Program of China (2022YFA1204800, 2023YFB360890 and 2021YFA0715502). This work was financially supported by the National Natural Science Foundation of China (62174064) and the Innovation Project of Optics Valley Laboratory (No. OVL2023ZD002).

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.