High wall-plug efficiency (WPE) micro-light-emitting diodes with metalorganic chemical vapor deposition-grown tunnel junction (TJ) contacts are demonstrated. By employing chemical treatments before sidewall activation, the 20 × 20 μm 2 TJ devices resulted in a voltage penalty of 0.2 V at 20 A cm −2 , compared to devices with indium-tin oxide (ITO) contacts. Moreover, the enhancement in light output power was more than 40% higher than ITO devices. Hence, the TJ devices yielded the peak external quantum efficiency (EQE) and WPE of 56% and 55%, respectively, indicating the improvements of 64% and 77% in peak EQE and WPE compared to ITO devices.

Improved turn-on voltages and reduced series resistances were realized by depositing highly Si-doped n-type GaN using molecular beam epitaxy on polarization-enhanced p-type InGaN contact layers grown using metal–organic chemical vapor deposition. We compared the effects of different Si doping concentrations and the addition of p-type InGaN on the forward voltages of p–n diodes and light-emitting diodes, and found that increasing the Si concentrations from 1.9 × 1020 to 4.6 × 1020 cm−3 and including a highly doped p-type InGaN at the junction both contributed to reductions in the depletion width, the series resistance of 4.2 × 10−3–3.4 × 10−3 Ω·cm2, and the turn-on voltages of the diodes.

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Blue semipolar vertical‐cavity surface‐emitting lasers with a buried tunnel junction current aperture are demonstrated under continuous‐wave operation with a differential efficiency of 4% and a threshold current of 2.7 mA for a lasing mode at 452 nm. The effects of the aperture diameter on these 9λ cavity length devices are presented, showing that the differential efficiency increases with aperture size, whereas the threshold current density remains constant for apertures larger than 10 μm. Filamentary lasing is observed in the larger aperture sizes, and it is suggested that this mode behavior is due to current injection inhomogeneity across the aperture. This theory is supported by the correlation between optical nearfield images and thermal microscopy images.

Violet semipolar (20-2-1) InGaN microcavity light-emitting diodes (MC-LED) with a 200 nm ultra-short cavity length were demonstrated. The emission wavelength was 419 nm with a spectrum width of 20 nm. The external quantum efficiency (EQE) of MC-LED was constant at 0.8% for a forward current from 0.5 to 2 mA with the emitting area of 30×30 µm2. With increasing forward current, the peak wavelength and spectrum width of the emission showed almost no changes. For epitaxial growth, metal-organic chemical vapor deposition (MOCVD) was used. Substrate removal and tunnel-junction with an Ag-based electrode made possible the fabrication of the ultra-short 200 nm thick cavity MC-LED. This is more than a factor of 2 improvement compared to previous MC-LEDs of 450 nm cavity thickness sustaining 5 modes.