Abstract
We have investigated the thermal characteristics of InGaN-based green micro-light-emitting diodes (micro-LEDs) without the passivation layer in a wide junction temperature range of 298–453 K. The decreased temperature coefficient (dVf/dT) of the device with a smaller device size is attributed to the increased series resistances for the smaller devices, largely affected by the defects due to sidewall damage of the active layer. The ideality factor of 2.02 at 298 K suggests that the charge transport mechanism could be defect-assisted tunneling. In addition, it is observed that the ideality factor decreases with increasing temperature. The results of the C–V measurements suggest similar electron and hole concentrations in the depletion region, leading to a balanced electron–hole recombination in the active layer. It was also found that the temperature-dependent bandgaps of ternary In0.3Ga0.7N obtained from electroluminescence spectra of micro-LEDs agree with the calculated values by using the semi-empirical Varshni relationship.
Highlights
Micro-light-emitting diodes have been spotlighted as a next-generation display technology, potentially providing better performance than their competitors such as liquid crystal displays (LCDs) and existing organic light-emitting diodes (OLEDs), due to the high resolution, wide color gamut, high brightness, fast response time, high stability, and long lifetime.1–4 In particular, there is high market demand for micro-LED micro-displays for virtual reality/augmented reality displays, which require high display resolutions and small scaled pixel pitches.5 many technical difficulties and challenges on the road to commercialization need to be overcome
The effect of temperature on the electrical characteristics, carrier density, and spectral properties of green InGaN micro-LEDs was systematically investigated in the junction-temperature range of 298–453 K. dVf /dT of the device increases with decreasing device size at fixed current
This is attributed to the larger series resistance of the smaller devices, which originated from the surface defect states due to the larger surface-to-volume ratio
Summary
Micro-light-emitting diodes (micro-LEDs) have been spotlighted as a next-generation display technology, potentially providing better performance than their competitors such as liquid crystal displays (LCDs) and existing organic light-emitting diodes (OLEDs), due to the high resolution, wide color gamut, high brightness, fast response time, high stability, and long lifetime. In particular, there is high market demand for micro-LED micro-displays for virtual reality/augmented reality displays, which require high display resolutions and small scaled pixel pitches. many technical difficulties and challenges on the road to commercialization need to be overcome. High junction temperature is caused by the heat generation inside the LED devices, which limits the optical output power, spectral efficiency, and lifetime.. We report a junction-temperature-dependent current density–voltage (J–V), capacitance–voltage (C–V), and optical characteristics of InGaN-based green micro-LEDs in a wide temperature range of 298–453 K. In the forward-voltage measurements, different pulse currents varying from 0.1 to 4 mA with a duty cycle of 0.1% (pulse width =5 ms and signal period =5 s) are injected into the microLED in a temperature-controlled oven. We assume that the junction temperature of the micro-LEDs is the same as the oven temperature because the pulse current with a very low duty cycle does not cause significant heating. The forward voltage drop was recorded using an Agilent B2912A for an oven temperature ranging from 298 to 453 K
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