Characteristics and applications of micro-pixelated GaN-based light emitting diodes on Si substrates

Using a GaN-based light emitting diode (LED) epitaxial structure grown on Si, individually addressable 10 × 10 micro-pixelated LED (μLED) arrays with pixel diameters of 45 μm and peak emission at ∼470 nm have been demonstrated. The electrical and optical properties of these μLEDs were compared with those of broad-area LEDs fabricated from the same epistructure. The μLEDs can sustain a much higher current density, up to 6.6 kA/cm2, before thermal rollover. Also, the fabricated μLEDs show good pixel-to-pixel uniformity, which demonstrates potential for low-cost micro-displays. Furthermore, these μLEDs demonstrate a high electrical-to-optical modulation bandwidth of up to ∼270 MHz and are suitable for visible light communication at data transmission rate up to 400 Mbit/s. The electrical-to-optical modulation bandwidth of the μLEDs increases rapidly with injection currents less than ∼6 mA, temporarily saturates at injection currents of ∼6 to ∼35 mA, and gradually increases again with injection currents up to 110 mA. Carrier density dependent recombination processes are responsible for the bandwidth increase at low current, the resistance-capacitance product determines the modulation bandwidth in the saturation region, and self-heating, which changes series resistance of μLEDs, may cause a further bandwidth increase at high current.