Dilute-antimonide GaSbN/GaN dots-in-wire heterostructures grown by molecular beam epitaxy: Structural and optical properties

We have investigated the epitaxy of GaSbN/GaN dots-in-wire heterostructures on a Si substrate by plasma-assisted molecular beam epitaxy. The photoluminescence (PL) emission wavelength was tuned from UV to blue and green regions at room temperature by varying the antimony (Sb) composition in the dilute regime (Sb concentration < 1%). Structural analysis reveals clearly defined interfaces between quantum-confined crystalline GaSbN and GaN layers with negligible lattice mismatch. The PL spectra unveil the non-monotonic dependence of the peak energy and linewidth on the excitation power and temperature. This can be correlated with the contributions from both localized and free excitons, wherein localized states dominate at low temperature and low excitation power. The screening of the quantum-confined Stark effect in the electroluminescence measurement suggests the presence of a substantially weaker built-in electric field (<240 kV/cm) for the green light emission at an ∼531 nm wavelength compared to conventional InGaN/GaN quantum wells, which is attributed to significantly reduced lattice mismatch between dilute-Sb GaSbN and GaN.