We have investigated the performance of AlGaInP-based red micro-light-emitting diodes (micro-LEDs) with different n-type contact schemes as functions of current, ambient temperature, and chip size. The samples with AuGe/Ni/Au contact revealed wider full width at half maximum of electroluminescence than that with the Pd/Ge contact. All samples also exhibited broad peaks at wavelengths between ∼632 and ∼640 nm, whose intensity depended on the type of contact schemes and temperature. Regardless of the contact schemes, the 10 μm-size samples showed a larger temperature-dependent reduction in the output power at current density of <50 A cm −2 than the 100 μm-size ones. Above 100 A cm −2 , however, both samples showed similar temperature dependence. Irrespective of the contact schemes, the main peak of the 100-μm samples was red-shifted, whereas no red-shift was detected in the 10-μm samples. The third peak of the AuGe-based contact samples became more dominant at 700 A cm −2 than the main peak, whereas that of the PdGe contact samples became more dominant at 1000 A cm −2 . Based on the chip size, current, contact scheme, and temperature dependence, the performance degradation of the red micro-LEDs is described and discussed.

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To enhance the light output of blue InGaN-based light emitting diodes (LEDs), a buried stripe-type n-electrode, expanded stripe-type p-electrode, and reflective p-bonding pad were employed. Flip-chip (FC) LEDs with the expanded p-electrode gave forward voltages of 2.99–3.11 V at 100 mA and series resistances of 3.28–3.94 Ω. The expanded p-electrode FCLED fabricated with 375 nm-thick window and TiO2 adhesion layers produced 22.7% higher light output at 21 A/cm2 than conventional FCLEDs. The expanded p-electrode FCLEDs revealed better current spreading efficiency than the c-FCLED, indicating the importance of the use of an optimised window and TiO2 adhesion layers.

The silicon (Si) or boron (B) implantation process in Ga0.8In0.2As/Ga x In1-x As y P1-y /Ga0.51In0.49P/GaAs quantum well structures can be used not only for maintaining single lateral mode during high power operation but also for increasing the catastrophic optical damage (COD) level of 980 nm pump lasers. The fabricated 980 nm pump lasers with partially ion implanted channels after ridge waveguide structure formation exhibited high power operation up to 250 mW without any kink and beam steering. A photoluminescence peak shift of 70 meV was obtained by 120 keV Si-implantation and annealing at 900°C. Improvement of the COD level by a minimum of 1.65 times is obtained by forming transparent windows near facets by Si implantation and annealing. A highly nonradiative polycrystalline phase of the active area may be the major cause of COD failure in the Al-free 980 nm lasers.