Abstract
We demonstrate that the concave-convex circular composite structure sidewall prepared by inductively coupled plasma (ICP) etching is an effective approach to increase the light efficiency without deteriorating the electrical characteristics for micro light-emitting diodes (LEDs). The saturated light output power of the device using the concave-convex circular composite structure sidewalls with a radius of 2 μm is 39.75 mW, an improvement of 7.2% compared with that of the device using flat sidewalls. The enhanced light output characteristics are primarily attributed to the increased photon emitting due by decreasing the total internal reflection without losing the active region area.
Highlights
With the developments of semiconductor technology and the maturity of miniaturization technology, more and more new applications of the light-emitting diodes (LEDs) have been realized [1,2,3,4,5,6,7].The various types of displays prepared by using mini- and micro-LEDs with a size of less than 300 μm as backlight units or self-emissive display units obtain new advantages in display technology attribute to their significant merits such as high resolution, low power consumption, long lifetime and short response time [8,9,10]
In order to satisfy the requirements of high dynamic range for new generation displays, it is still necessary to improve the light efficiency of the micro-LED unit because the brightness of displays should be above 1000 nits [11]
The light output power (LOP) of micro-LEDs is not high enough owing to the low external quantum efficiency (EQE), which is mainly limited by the high total internal reflection (TIR)
Summary
The various types of displays prepared by using mini- and micro-LEDs with a size of less than 300 μm as backlight units or self-emissive display units obtain new advantages in display technology attribute to their significant merits such as high resolution, low power consumption, long lifetime and short response time [8,9,10]. In order to satisfy the requirements of high dynamic range for new generation displays, it is still necessary to improve the light efficiency of the micro-LED unit because the brightness of displays should be above 1000 nits [11]. The light output power (LOP) of micro-LEDs is not high enough owing to the low external quantum efficiency (EQE), which is mainly limited by the high total internal reflection (TIR). Sidewall can be increased by reducing the TIR, thereby realizing the improvement of light extraction efficiency (LEE) and light efficiency [14,15,16]. Several advantageous approaches have been put forward to increase the LEE, such as patterned sapphire substrates [17,18,19], textured surfaces [19,20,21,22], SiO2
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