Performance improvement of GaN-based microdisk lasers by using a PEALD-SiO₂ passivation layer

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Dry-etching of Gallium Nitride (GaN)-based materials introduces sidewall defects, acting as non-radiative recombination centers and charge traps.
• These defects degrade the performance of GaN-based devices, particularly lasers.

Purpose of the Study:

• To investigate the impact of dielectric films deposited by plasma-enhanced atomic layer deposition (PEALD) and plasma-enhanced chemical vapor deposition (PECVD) on GaN-based microdisk laser performance.
• To compare the effectiveness of PEALD-SiO2 and PECVD-Si3N4 passivation layers in mitigating dry-etching-induced defects.

Main Methods:

• Deposition of dielectric films (SiO2 and Si3N4) using PEALD and PECVD techniques.
• Fabrication and characterization of GaN-based microdisk lasers with different passivation layers.
• Analysis of device performance metrics including threshold current, luminescence efficiency, and size dependence.

Main Results:

• The PEALD-SiO2 passivation layer significantly reduced trap-state density in GaN-based microdisk lasers.
• Non-radiative recombination lifetime was notably increased by the PEALD-SiO2 layer.
• Compared to PECVD-Si3N4, PEALD-SiO2 resulted in a decreased threshold current, enhanced luminescence efficiency, and reduced size dependence.

Conclusions:

• PEALD-SiO2 is a superior passivation material for GaN-based microdisk lasers compared to PECVD-Si3N4.
• Effective passivation of sidewall defects is crucial for improving the performance and reliability of GaN-based optoelectronic devices.