Tunable light-emission through the range 1.8-3.2 eV and p-type conductivity at room temperature for nitride semiconductors, Ca(Mg1-xZnx)2N2 (x=0-1)

TL;DR

This study demonstrates tunable light emission and p-type conductivity in Ca(Mg1-xZnx)2N2 nitride semiconductors, with adjustable band gaps from 1.8 to 3.2 eV, achieved through synthesis and doping, suitable for optoelectronic applications.

Contribution

It provides experimental validation of theoretical predictions for band gap tuning via Mg substitution and introduces p-type doping to achieve efficient green light emission.

Findings

Band gap tunability from 1.8 to 3.2 eV confirmed experimentally.

Na doping induces p-type conductivity in CaZn2N2.

Green emission at 2.45 eV observed in x=0.50 sample.

Abstract

The ternary nitride CaZn2N2, composed only of earth-abundant elements, is a novel semiconductor with a band gap of 1.8 eV. First-principles calculations predict that continuous Mg substitution at the Zn site will change the optical band gap in a wide range from ~3.3 eV to ~1.9 eV for Ca(Mg1-xZnx)2N2 (x = 0-1). In this study, we demonstrate that a solid-state reaction at ambient pressure and a high-pressure synthesis at 5 GPa produce x = 0 and 0.12, and x = 0.12-1 polycrystalline samples, respectively. It is experimentally confirmed that the optical band gap can be continuously tuned from ~3.2 eV to ~1.8 eV, a range very close to that predicted by theory. Band-to-band photoluminescence is observed at room temperature in the ultravioletfired region depending on x. A 2% Na doping at the Ca site of CaZn2N2 converts its highly resistive state to a p-type conducting state. Particularly, the x = 0.50 sample exhibits intense green emission with a peak at 2.45 eV (506 nm) without any other emission from deep-level defects. These features meet the demands of the III-V group nitride and arsenide/phosphide light-emitting semiconductors.