Nitrogen doped ultrananocrystalline diamond conductive layer grown on InGaN-based light-emitting diodes using nanopattern enhanced nucleation

Highlights: • Nitrogen doped ultrananocrystalline diamond conductive layer on nanopatterned InGaN-LEDs. • Nucleation density of N-UNCD is increased significantly on InGaN-LED with concave nanopattern. • Quantum confined Stark effect is diminished significantly in N-UNCD/nanopatterned InGaN-LED. This study grew nitrogen doped ultrananocrystalline diamond (N-UNCD) conductive layer on InGaN-based light emitting diodes (LEDs) using the concave nanopattern (CNP) enhanced nucleation. The low nucleation density of the N-UNCD on bare LEDs (Br-LED) resulted in an island morphology. The nucleation density of the N-UNCD increased significantly from 1.8 × 10⁸ cm⁻² for Br-LED to 3.6 × 10⁹ cm⁻² for LEDs with a CNP density of 6.1 × 10⁹ cm⁻² (CNP-LED). The N-UNCD preferred to nucleate inside the CNP during the initial growth stage. The N-UNCD islands then merged and grew laterally to form a continuous thin film within a thickness of 300 nm. The N-UNCD/CNP-LED exhibited a stable electroluminescence peak wavelength of ~447.1 nm in the injection current range of 10–100 mA. The decrease in the compressive stress due to removing the p-GaN layer (i.e. the CNP structure) resulted in a quantum confined Stark effect (QCSE) mitigation in the multi-quantum wells (MQWs). In addition, the lower turn on voltage caused a lower electric field in the MQWs and diminished the screen of the QCSE. The N-UNCD prepared by the proposed nucleation technique demonstrated a promising conductive layer for InGaN-based LEDs.