Europium-Implanted AlN Nanowires for Red Light-Emitting Diodes

Europium (Eu)-implanted AlN nanowire (NW) pn junctions, subjected to rapid thermal annealing at 1000 degrees C, were investigated in view of application as red light-emitting diodes (LEDs). In a first step, the structural and optical properties of NWs implanted with two different fluences (1 x 10(14) cm(-2) and 5 x 10(14) cm(-2)) were studied. The luminescence of the trivalent Eu ions (Eu3+) was achieved for both samples using below and above AlN bandgap energy excitation. The excitation below the AlN bandgap occurs through two broad bands, A1 (peaked at similar to 270 nm) and A2 (peaked at similar to 367 nm), associated with lattice defects. In addition to Eu3+ luminescence, other radiative channels linked to deep-level defects were identified in photoluminescence (PL). The cathodoluminescence (CL) relative intensity ratio between intraionic and defect-related emissions increases compared to that of PL. In both PL and CL, the Eu3+ luminescence intensity increases about three times for the highest fluence, while the contribution from radiative recombination at defects decreases. This study also allowed to map an in-depth profile of the optically active Eu3+, revealing that it extends deeper than the range predicted by Monte Carlo simulations. Based on these findings, a proof-of-concept red LED is shown using the NWs implanted with the highest fluence. The devices exhibited the typical rectifying behavior of a p-n junction and an electroluminescence signal dominated by the D-5(0) -> F-7(2) transition (similar to 624 nm) starting at a threshold voltage of 12 V. The demonstration of red LEDs based on Eu-implanted AlN NWs highlights the potential of such an approach for developing multi-color nano-emitters.

Automated summary

Europium-implanted AlN nanowire pn junctions were annealed at 1000 degrees C and showed increased Eu3+ luminescence intensity with higher fluence, while the contribution from defect-related emissions decreased. This study demonstrates the potential of using Eu-implanted AlN NWs for developing red LEDs with improved luminescence properties.