Quantum-Tuned Cascade Multijunction Infrared Photodetector

Emerging applications such as augmented reality, self-driving vehicles, and quantum information technology require optoelectronic devices capable of sensing a low number of photons with high sensitivity (including gain) and high speed and that could operate in the infrared at telecom windows beyond silicon's bandgap. State-of-the-art semiconductors achieve some of these functions through costly and not easily scalable doping and epitaxial growing methods. Colloidal quantum dots (QDs), on the other hand, could be easily tuned and are compatible with consumer electronics manufacturing. However, the development of a QD infrared photodetector with high gain and high response speed remains a challenge. Herein, we present a QD monolithic multijunction cascade photodetector that advances in the speed-sensitivity-gain space through precise control over doping and bandgap. We achieved this by implementing a QD stack in which each layer is tailored via bandgap tuning and electrostatic surface manipulation. The resulting junctions sustain enhanced local electric fields, which, upon illumination, facilitate charge tunneling, recirculation, and gain, but retain low dark currents in the absence of light. Using this platform, we demonstrate an infrared photodetector sensitive up to 1500 nm, with a specific detectivity of similar to 3.7 x 10(12) Jones, a 3 dB bandwidth of 300 kHz (0.05 cm(2) device), and a gain of similar to 70x at 1300 nm, leading to an overall gain-bandwidth product over 20 MHz, in comparison with 3 kHz of standard photodiode devices of similar areas.

Automated summary

In this study, we developed a QD monolithic multijunction cascade photodetector with high gain and high response speed by controlling the bandgap and electrostatic surface of QDs. The detector achieved high sensitivity to infrared light up to 1500 nm wavelength, with a specific detectivity of 3.7 x 10^12 Jones, a 3 dB bandwidth of 300 kHz (0.05 cm^2 device), and a gain of approximately 70x at 1300 nm. Compared to standard photodiode devices, the QD photodetector exhibited a significantly higher gain-bandwidth product over 20 MHz.