Ultrafast Broadband Photodetectors based on Three-dimensional Dirac Semimetal Cd3As2 (1609.00768v1)

Abstract: The efforts to pursue photo detection with extreme performance in terms of ultrafast response time, broad detection wavelength range, and high sensitivity have never been exhausted as driven by its wide range of optoelectronic and photonic applications such as optical communications, interconnects, imaging and remote sensing1. 2D Dirac semimetal graphene has shown excellent potential toward high performance photodetector with high operation speed, broadband response and efficient carrier multiplications benefiting from its linear dispersion band structure with high carrier mobility and zero bandgap2-4. As the three dimensional analogues of graphene, Dirac semimetal Cd3As2 processes all advantages of graphene as a photosensitive material but potentially has stronger interaction with light as bulk material and thus enhanced responsivity5,6, which promises great potential in improving the performance of photodetector in various aspects . In this work, we report the realization of an ultrafast broadband photodetector based on Cd3As2. The prototype metal-Cd3As2-metal photodetector exhibits a responsivity of 5.9 mA/W with response time of about 6.9 ps without any special device optimization. Broadband responses from 0.8 eV to 2.34 eV are measured with potential detection range extendable to far infrared and terahertz. Systematical studies indicate that the photo-thermoelectric effect plays important roles in photocurrent generation, similar to that in graphene. Our results suggest this emerging class of exotic quantum materials can be harnessed for photo detection with high sensitivity and high speed (~145 GHz) in challenging middle/far-infrared and THz range.

Ultrafast Broadband Photodetectors Based on Three-Dimensional Dirac Semimetal Cd₃As₂

The investigation into high-performance photodetectors remains pivotal due to their extensive application in optoelectronic and photonic domains. This paper explores the fabrication and performance of a novel photodetector using a three-dimensional (3D) Dirac semimetal, Cd₃As₂, which presents enhanced optoelectronic properties and an ultrafast photoresponse. Cd₃As₂ stands out by possessing all the advantageous traits of two-dimensional (2D) Dirac materials like graphene, such as high carrier mobility and efficient carrier multiplication, but promises even greater interaction with light due to its bulk nature.

The paper begins by highlighting the intrinsic advantages of 3D Dirac semimetals, emphasizing Cd₃As₂. The earlier focus in this material's research was primarily directed at its electronic transport properties, as evidenced by phenomenons such as giant magnetoresistance and Landau level splitting. However, the photonic and optoelectronic potentials of Cd₃As₂ remained largely unexplored until the presented paper.

Through experimental design, the authors describe the chemical vapor deposition method used for synthesizing Cd₃As₂ nanowires and nanoplates. They then detail the fabrication of metal-Cd₃As₂-metal devices demonstrating a significant photothermoelectric (PTE) effect, instrumental in ultrafast carrier dynamics. The paper reports a remarkable responsivity of 5.9 mA/W and an ultrafast response time of about 6.9 ps, showcasing the device's potential for applications demanding rapid photoresponse.

Significantly, the devices show a broadband response from 0.8 eV to 2.34 eV, meaning their potential detection range could be extended to far-infrared and terahertz domains. This performance is attributed in part to the efficient PTE effect observed in these materials, akin to that seen in graphene, involving hot carrier generation and subsequent photo voltage production through electron temperature gradients.

The results from spatially resolved scanning photocurrent microscopy (SPCM) and time-resolved photocurrent spectroscopy (TRPC) indicate the photoresponse time of a Cd₃As₂-based photodetector aligns with the high-speed requirements of contemporary optoelectronic applications, demonstrating the device's capability near terahertz operation speeds. This performance is consistent regardless of geometrical variations in the device structure, implying robustness and reliability.

The research posits that the gapless band structure inherent in Cd₃As₂, apart from promoting broadband photoresponse, also enhances responsivity due to phenomena like carrier multiplication. The paper outlines a comparison with graphene, indicating that while 3D Cd₃As₂ might not yet achieve the highest responsivities seen in graphene through specific optimizations, it does provide significant light interaction benefits unavailable to atomically-thin graphene.

The presented work implies substantial future development prospects for 3D Dirac semimetals as a material platform in broadband, high-speed photodetection, particularly in the middle and far infrared as well as terahertz spectral ranges. Encouragingly, the potential scalability through molecular beam epitaxial growth techniques could enhance large-scale integration of these devices in various optoelectronic applications, thereby directly impacting technological advancements in fields such as high-speed optical communications and remote sensing.

In conclusion, this research postulates that 3D Dirac semimetals like Cd₃As₂ offer promising pathways to achieving ultrafast, broadband photodetection with high sensitivity, encouraging further exploration and application of these materials in diverse optoelectronic systems.