Eu3+ optical activation engineering in AlxGa1-xN nanowires for red solid-state nano-emitters

In this work, Eu3+-implanted and annealed AlxGa1-xN (0 ≤ x ≤ 1) nanowires (NWs) grown on GaN NW template on Si (111) substrates by plasma-assisted molecular beam epitaxy are studied by µ-Raman, cathodoluminescence (CL), nano-CL, and temperature-dependent steady-state photoluminescence (PL). The preferential location of the Eu3+-implanted ions is found to be at the AlxGa1-xN top-section. The recovery of the as-grown crystalline properties is achieved after rapid thermal annealing (RTA). After RTA, the red emission of the Eu3+ ions is attained for all the samples with below and above bandgap excitation. The 5D0 → 7F2 transition is the most intense one, experiencing a redshift with increasing AlN nominal content (x) from GaN to AlN NWs. Moreover, AlN nominal content and annealing temperature alter its spectral shape suggesting the presence of at least two distinct optically active Eu3+ centers (Eu1 and Eu2). Thermal quenching of the Eu3+ ions´ luminescence intensity, I, is determined for all the samples from 14 K to 300 K, being the emission of Eu3+-implanted AlN NWs after RTA at 1200 °C the most stable (I300 K/I14 K ~80%). The GaN/AlN interface in this sample is also found to have a key role in the Eu3+ optical activation.