Strain Engineering to Release Trapped Hole Carriers in p-Type Haeckelite GaN

The gallium nitride haeckelite (418-GaN) phase is an attractive material for a two-dimensional (2D) light-emitting diode (LED); however, its p-type doping is still challenging due to hole carrier trapping. Our density functional theory calculations suggest strain engineering as a route to release trapped hole carriers. We show that Mg and Be impurities in 418-GaN have multifarious hole states, including symmetry-broken polaronic (trapped) and delocalized (extended) states, whose detrapping energies are estimated to be 33.4 and 263.3 meV for Mg and Be impurities, respectively. The hole states trapped by a Mg impurity can be, however, detrapped by applying a moderate tensile strain around 2% perpendicular to the 418 plane, which would critically enhance p-type dopability. We further show that the photoluminescence (PL) spectrum of a Mg impurity can be tuned by the lattice strain, which enables efficient control for light emission of 418-GaN. Our findings pave the way to design an atomically thin blue LED based on 418-GaN.

Automated summary

This study suggests that strain engineering can release trapped hole carriers in gallium nitride materials, solving the challenge of p-type doping. Additionally, the photoluminescence spectrum of magnesium impurities can be tuned by lattice strain, allowing for efficient control of gallium nitride light emission.