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Thin Si-doped Al-rich (xAl > 0.85) regrown Al(Ga)N layers were deposited on AlN on sapphire template using metal-organic chemical vapor deposition (MOCVD) techniques. The optimization of the deposition conditions, such as temperature (1150 °C), V/III ratio (750), deposition rate (0.7 Å/s), and Si concentration (6 × 10^19/cm3), resulted in a high charge carrier concentration (> 10^15 cm−3) in the Si-doped Al-rich Al(Ga)N films. A pulsed deposition condition with pulsed triethylgallium and a continuous flow of trimethylaluminum and ammonia was employed to achieve a controllable Al composition xAl > 0.95 and to prevent unintended Ga incorporation in the AlGaN material deposited using the close-coupled showerhead reactor. Also, the effect of unintentional Si incorporation on free charge carrier concentration at the regrowth interface was studied by varying the thickness of the regrown Al(Ga)N layer from 65 to < 300 nm. A maximum charge carrier concentration of 4.8 × 10^16 and 7.5 × 10^15/cm3 was achieved for Al0.97Ga0.03N and AlN films with thickness <300 nm compared to previously reported n-Al(Ga)N films with thickness ≥400 nm deposited using MOCVD technique. 

UV‐ranged micro‐LEDs are being explored for numerous applications due to their high stability and power efficiency. However, previous reports have shown reduced external quantum efficiency (EQE) and increased leakage current due to the increase in surface‐to‐volume ratio with a decrease in the micro‐LED size. Herein, the size‐related performance for UV‐A micro‐LEDs, ranging from 8 × 8 to 100 × 100 μm², is studied. These devices exhibit reduced leakage current with the implementation of atomic layer deposition‐based sidewall passivation. A systematic EQE comparison is performed with minimal leakage current and a size‐independent on‐wafer EQE of around 5.5% is obtained. Smaller sized devices experimentally show enhanced EQE at high current density due to their improved heat dissipation capabilities. To the best of authors’ knowledge, this is the highest reported on‐wafer EQE demonstrated in <10 μm dimensioned 368 nm UV LEDs.