(A) study on quantum dot size adjustment for efficient electro-kinetic multiplication in infrared photodetector

Abstract

Colloidal quantum dots (CQDs) are promising materials for infrared photodetector (IRPD) because of their high absorption coefficients, size-tunable characteristics, and cost-effective fabrication techniques. Nevertheless, relatively low detectivity (D$^*$) exhibited by CQD-based IRPDs has spurred investigations into kinetically-pumped CQD-based IRPDs for boosting detectivity (D$^*$). An accompanying challenge, however, is the unintended surge in flicker noise (1/f noise) induced by the carrier multiplication in the device, which is attributable to the discrete energy levels from energy level overlapping along with the trap densities controlled by the CQD size. Such CQD size adjustments not only alter noise level but also affect the threshold voltage required for impact ionization, where the trade-off relationship occurs between the size-dependent noise and current gain characteristics. Our device features an optimal absorption wavelength (1S$_{max}$) of 920 nm in multiplication layer, demonstrating a maximum responsivity of 17.98 kA/W, a dark current noise of 54.7 nA, a bandwidth of 7.5×10$^5$ Hz, and a final detectivity of 1.1×10$^14$ Jones. Furthermore, our findings also offer valuable insights into the design parameters offering advanced N-I-P and SACM (separated-absorption-charge-multiplication) structures that could pave the way of developing the high-performance of kinetically-pumped CQD-based IRPDs.