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

Tian, Pengfei and McKendry, Jonathan and Gong, Zheng and Zhang, Shuailong and Watson, Scott and Zhu, Dandan and Watson, Ian and Gu, Erdan and Kelly, Anthony E and Humphreys, Colin J and Dawson, Martin (2014) Characteristics and applications of micro-pixelated GaN-based light emitting diodes on Si substrates. Journal of Applied Physics, 115 (3). ISSN 0021-8979

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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.