Atomic Layer Deposition for Stable InP-Based On-Chip Quantum Dot microLEDs: Hybrid Quantum Dot Pockets

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Indium phosphide (InP) quantum dots (QDs) offer a non-toxic alternative to cadmium-based QDs for quantum dot LEDs (QLEDs).
• QLEDs face challenges with luminescence degradation due to ambient air exposure, necessitating protective encapsulation strategies.
• Hybrid barrier layers, combining organic and inorganic materials, are explored to enhance QD stability.

Purpose of the Study:

• To investigate the effectiveness of atomic layer deposition (ALD) for encapsulating InP-based QDs with metal oxide thin films.
• To evaluate the photoluminescence (PL) stability of ALD-coated InP QDs, both as thin films and embedded in polymers.
• To assess the potential of hybrid QD structures for developing stable, on-chip quantum dot microLEDs.

Main Methods:

• Deposition of Al2O3, TiO2, and ZnO thin films via ALD using trimethylaluminum (TMA), tetrakis(dimethylamino)titanium (TDMAT), and diethylzinc (DEZ) precursors, respectively, with H2O reactant.
• In situ photoluminescence (PL) measurements during ALD coating to monitor optical response.
• Accelerated degradation testing in a humidity chamber at elevated temperatures to assess long-term stability.
• Fabrication of UV-patterned polymer (thiol-ene) QD pockets for on-chip microLED applications.

Main Results:

• ALD coating degraded luminescence on pristine InP QD thin films but not on polymer-embedded QDs.
• A single Al2O3 ALD film provided enhanced PL stability (>300 h) for polymer-embedded QDs compared to pristine samples.
• Hybrid QD pockets with Al2O3 ALD films showed significantly improved PL stability, with no degradation observed after 140 h.

Conclusions:

• Polymer embedding combined with ALD encapsulation is an effective strategy for improving the long-term stability of InP-based QDs.
• The QD pocket structure offers a scalable approach for manufacturing stable on-chip quantum dot microLEDs.
• This hybrid approach shows significant promise for the development of robust and reliable InP-based optoelectronic devices.