2D-GaN/AlN Multiple Quantum Disks/Quantum Well Heterostructures for High-Power Electron-Beam Pumped UVC Emitters.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Gallium nitride/aluminum nitride (GaN/AlN) heterostructures are crucial for developing efficient ultraviolet-C (UVC) light emitters.
• Achieving tunable emission wavelengths and high output power in UVC devices remains a key challenge.

Purpose of the Study:

• To investigate the growth and optical properties of multi-period GaN/AlN quantum disk/well heterostructures.
• To explore the influence of growth parameters, specifically the gallium to activated nitrogen flux ratio (Ga/N₂*), on material topography and emission characteristics.
• To demonstrate high-power UVC emission from these engineered heterostructures.

Main Methods:

• Plasma-assisted molecular-beam epitaxy (PAMBE) was employed to grow GaN/AlN heterostructures with up to 400 periods on c-sapphire substrates.
• The 2D topography and growth modes were controlled by varying the Ga/N₂* flux ratio.
• Emission properties were characterized by photoluminescence and electron-beam pumping.

Main Results:

• A transition from mixed spiral and 2D-nucleation growth to purely spiral growth was observed with increasing Ga/N₂* ratio.
• Emission energy was tuned from 5.21 eV (238 nm) to 4.68 eV (265 nm) by controlling carrier localization.
• Electron-beam pumping yielded a maximum output optical power of 50 W at 265 nm and 10 W at 238 nm.

Conclusions:

• The Ga/N₂* flux ratio is a critical parameter for controlling the growth mode and achieving tunable emission in GaN/AlN heterostructures.
• These engineered heterostructures show significant potential for high-power UVC emitter applications.
• The demonstrated tunability and power output represent a substantial advancement in UVC optoelectronics.