T2.4 High Carrier Mobility in HgTe Quantum Dot Solids Improves Mid-IR Photodetectors
Menglu Chen (University of Chicago)
Improving charge mobility in quantum dot (QD) films is important for device performance, where high mobility helps to improve efficiency of photodetectors, solar cells, and LEDs. However, these applications also require preserving well-defined quantum dot electronic states and optical transitions. We present HgTe QD films which show the highest mobility yet achieved for transport through discrete QD states. A novel hybrid surface passivation process efficiently eliminates surface states, provides tunable air-stable n and p-doping, and enables hysteresis-free filling of QD states evidenced by strong conductance modulation. QD films dried at room temperature without any post treatments exhibit mobility up to μ ~ 8 cm2V-1s-1 at low carrier density of less than one electron per QD, bandlike (∂μ/∂T < 0) behavior down to 70 K, similar drift and Hall mobilities at all temperatures. We compare the photoconductive properties with the prior “solid-state ligand exchange” using ethanedithiol, and we find that the new process affords a ∼100-fold increase of the electron and hole mobility, a ∼100-fold increase in responsivity, and a ∼10-fold increase in detectivity. These photodetector improvements are primarily attributed to the increase in mobility because the optical properties are mostly unchanged. We show that the specific detectivity (D*) of a photoconductive device is expected to scale as μ1/2. The application potential is further verified by long-term device stability.
Event Timeslots (1)
SYMPOSIUM T2 – MATERIALS PROCESSING AND CHEMISTRY
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Menglu Chen
Location: Technological Institute M177