Efficiency and Droop Improvement in GaN-Based High-Voltage Light-Emitting Diodes

An Estimation Method for the Efficiency of Light-Emitting Diode (LED) Devices

“…Injection current is another important factor of efficiency droop [14], [15]. The efficiencies of LEDs with microchips of varying sizes were experimentally compared in [14].…”

“…The efficiencies of LEDs with microchips of varying sizes were experimentally compared in [14]. The experimental results presented the noteworthy effect of current density on efficiency droop [14].…”

“…The efficiencies of LEDs with microchips of varying sizes were experimentally compared in [14]. The experimental results presented the noteworthy effect of current density on efficiency droop [14]. Carrier loss mechanisms, including auger recombination [16], [17], carrier leakage [18], carrier delocalization [19], and electron overflow [20], [21], are known to be the cause of injection current that results in efficiency droop.…”

Optimized Process and Tool Design for GaN Chemical Mechanical Planarization

“…It is designed into the light emitting diodes (LEDs) and ultraviolet LED (UVLED) manufacturing as an active region. 5,6 These applications require the polishing and optimal planarization of the GaN layers where CMP is the method of choice due to enabling nano-scale smoothness on the wafer surfaces in addition to enabling material and topographic selectivity through advanced slurry formulations.7 Yet, the main problem in integration of GaN is related to the challenges in its defect free deposition and its hard and brittle nature, which makes it difficult to polish and planarize in an integration scheme without creating surface defectivity, which can be defined as the elevated surface roughness, scratches, local pitting and protrusions, slurry particles and particles from the surroundings that might be left on the wafer surface.The growth of thick and crystalline GaN films is very challenging due to the formation of the threading dislocations between the selected substrate and the GaN interface that can act as the short-circuit leakage paths.1 Furthermore, it is also known that GaN films tend to crack above a critical thickness, which can even lead to the film and the substrate to fracture into separate pieces.8 Many conventional deposition techniques fail to satisfy the defect free deposition of GaN on conventional substrates such as silicon. Therefore, substrates such as ZnO and SiC are experimented which have the same crystal structure as GaN (wurtzite).…”

“…It is designed into the light emitting diodes (LEDs) and ultraviolet LED (UVLED) manufacturing as an active region. 5,6 These applications require the polishing and optimal planarization of the GaN layers where CMP is the method of choice due to enabling nano-scale smoothness on the wafer surfaces in addition to enabling material and topographic selectivity through advanced slurry formulations.…”