Harnessing III-Nitride Built-In Field in Multi-Quantum Well LEDs

Area of Science:

• Semiconductor physics
• Materials science
• Optoelectronics

Background:

• III-nitride materials, like gallium nitride (GaN), are crucial for light-emitting devices.
• The wurtzite crystal structure in III-nitrides causes significant polarization fields.
• These fields, coupled with high acceptor ionization energy, hinder carrier injection and distribution in quantum well (QW) LEDs.

Purpose of the Study:

• To investigate and compare carrier distribution in Ga-polar LEDs.
• To analyze two configurations: standard "p-up" and inverted "p-down" using a bottom-tunnel junction.
• To understand the impact of inverted layer sequences on carrier transport and device performance.

Main Methods:

• Fabrication and characterization of Ga-polar LEDs in "p-up" and "p-down" configurations.
• Utilizing a bottom-tunnel junction to invert the p- and n-layer sequence.
• Employing color-coded, alternating quantum wells (QWs) to probe carrier distribution.

Main Results:

• Carrier transport in "p-down" LEDs is limited by the potential barrier at the QW interface.
• In contrast, hole mobility is identified as the bottleneck for carrier transport in "p-up" structures.
• "P-down" LED configurations demonstrate a significantly reduced turn-on voltage.

Conclusions:

• The "p-down" configuration offers an effective strategy to mitigate carrier transport issues in III-nitride LEDs.
• Inverted structures can overcome limitations associated with inherent polarization fields.
• The observed low turn-on voltage in "p-down" LEDs suggests potential for enhanced device efficiency.