Symmetric Injection of Electrons and Holes in III-Nitrides LEDs through Point Defect Engineering: Ab Initio Nonadiabatic Molecular Dynamics Study

Gallium nitride (GaN) is a critical semiconductor in modern technology, particularly for solid-state lighting and power electronics. The quantum efficiency of GaN-based ultraviolet (UV) LEDs is limited to below 10% due to asymmetric carrier injection. Our research employs advanced NAMD-EPC methods to demonstrate that slow hot electron cooling in GaN is linked to its conduction band structure and weak phonon-assisted processes. The quasi-energy gap (Eg2) of 2.54 eV between the conduction band minimum (CBM) and higher bands results in a low density of states, limiting state continuity and restricting phonon excitations during electron cooling.

To enhance hot electron cooling, we propose defect engineering in GaN/AlN quantum wells to achieve symmetrical carrier injection. By introducing specific point defects, we aim to improve the density of states and promote phonon excitations that help with electron relaxation. Our findings show that nitrogen vacancies (VN) in the quantum barrier layers near the interface create three defect states, significantly accelerating the hot electron cooling process. Electron relaxation times decrease from 8.61 ps to 0.016 ps. Using Huang's formula, we establish that defect states enhance the density of states in the Eg2 region and activate weak phonon modes, improving electron-phonon coupling. This approach is also applicable to InN/GaN quantum wells, further highlighting its potential to advance the efficiency of nitride-based devices.