Cd_1-MgS CQD thin films for high performance and highly selective NIR photodetection

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Development of high-performance near-infrared (NIR) photodetectors (PDs) is crucial for various applications.
• Wide band gap semiconductors are actively researched for NIR PDs, but cost-effective fabrication remains a challenge.

Purpose of the Study:

• To demonstrate a cost-effective and easily fabricated NIR photodetector (PD) using Mg-doped CdS colloidal quantum dots (CQDs).
• To investigate the influence of Mg doping on the transport properties and performance of CdS CQD films for PD applications.
• To tune the sensing range and improve the selectivity of NIR PDs.

Main Methods:

• Thin films of Cd$_{1-x}$Mg$_{x}$S (where x = 0 to 0.05) colloidal quantum dots (CQDs) were fabricated.
• Device performance was evaluated under laser illumination at various wavelengths (405 nm to 782 nm).
• Key performance parameters including response time, responsivity, photosensitivity, quantum efficiency, and specific detectivity were measured.

Main Results:

• Mg doping improved photoresponsivity beyond the intrinsic absorption range of CdS.
• The Mg-doped CdS CQD PDs exhibited enhanced performance metrics: response time (110 ms), responsivity (∼26.9 A W$^{-1}$), photosensitivity (∼4.7 × 10$^{4}$%), quantum efficiency (∼41.23%), and specific detectivity (∼3.45 × 10$^{13}$ Jones).
• The sensing range was tuned from visible (650 nm) to NIR (782 nm) with improved selectivity due to Mg incorporation.

Conclusions:

• Cost-effective and easy fabrication of NIR PDs is achievable using Mg-doped CdS CQDs.
• Mg doping significantly enhances the performance and selectivity of NIR PDs.
• These devices offer competitive figures of merit compared to those fabricated using complex methods.