Efficiency enhancement of AlGaInP-based red mini-LEDs by a HfO₂-based hybrid passivation layer

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• AlGaInP-based red mini light-emitting diodes (mini-LEDs) face challenges with low light extraction efficiency (LEE) and external quantum efficiency (EQE) due to conventional passivation materials and sidewall defects.
• The low refractive index of existing passivation layers limits light emission, hindering overall device performance.

Purpose of the Study:

• To introduce and evaluate a novel Hafnium Oxide (HfO2)-based hybrid passivation layer for AlGaInP-based red mini-LEDs.
• To improve the light extraction efficiency (LEE) and external quantum efficiency (EQE) of mini-LEDs through optimized passivation strategies.

Main Methods:

• Fabrication of a hybrid passivation layer consisting of atomic-layer-deposited (ALD) HfO2, ALD-Al2O3, and plasma-enhanced-chemical-vapor-deposited SiO2.
• Integration of the HfO2-based hybrid passivation layer onto AlGaInP-based mini-LED structures.
• Characterization of optical and electrical performance, including LEE and EQE measurements, supported by simulations.

Main Results:

• Simulations predicted a 15.1% increase in LEE for mini-LEDs utilizing the HfO2-based hybrid passivation layer.
• Experimental results demonstrated a peak external quantum efficiency (EQE) of 20.19% at 5 mA.
• The HfO2-based hybrid passivation layer achieved a 6.7% improvement in EQE compared to devices without it.

Conclusions:

• The HfO2-based hybrid passivation layer offers a compatible refractive index with AlGaInP, enhancing light emission angles and improving LEE.
• This novel passivation strategy provides a scalable solution for developing high-performance mini-LEDs.
• The findings pave the way for advancing display technologies through improved optoelectronic device efficiency.