Negative photoconductivity-driven interface engineering in topological insulator BiSb/InP heterojunctions for...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Conventional indium phosphide (InP) photodetectors exhibit limited performance in the ultraviolet-visible spectrum, hindering their application in broadband optical communication.
• Developing photodetectors with extended spectral response is crucial for advanced optical systems.

Purpose of the Study:

• To engineer a novel heterojunction architecture for broadband ultraviolet-visible-infrared photodetectors.
• To overcome the spectral limitations of traditional InP-based photodetectors.

Main Methods:

• Integration of topological insulator Bismuth Antimony (BiSb) with an InP substrate using (012)-oriented preferential growth.
• Leveraging type-II band alignment and Dirac surface states for enhanced carrier transport.
• Implementing a negative photoconductance (NPC) mechanism to suppress photocarrier trapping.
• Utilizing Density Functional Theory (DFT) for interfacial physics analysis.

Main Results:

• Achieved efficient carrier transport and tunable broadband light capture via Dirac surface states.
• Demonstrated selective suppression of low-energy photocarrier trapping using NPC.
• DFT calculations revealed an interfacial dipole of 0.18 eV optimizing carrier transport.
• Exhibited dual-band synergy with responsivities of 5.75 mA/W at 365 nm and 10 mA/W at 650 nm.
• Reported fast response times (0.4/1.76 ms rise/fall) and low photocurrent at 365 nm.

Conclusions:

• Pioneered the integration of topological surface state engineering with NPC modulation on industrial InP platforms.
• Developed a scalable solution for high-sensitivity multispectral imaging and high-speed optical communication.
• The novel heterojunction architecture significantly enhances photodetector performance across a broad spectrum.