Table 5.

Summary of the effect of doping materials and substrate modification of NUV LEDs’ primary optics.

Methods	Noticeable Improvement	Ref.
Eutectic flip chip NUV LED with a aluminum nitride nanoparticle (AlN NP)-doped silicon layer as primary optics material	The Light output power has been increased by 17.4% with a reduction in junction temperature by 5.7 °C compared to the silicon layer.	[102]
Controlling the eutectic voidage of eutectic flip chip NUV LED (void reduction from 30% to 3%)	The Light power has been enhanced by 13.3% with a reduction in junction temperature by 3.5 °C due to the void reduction from 30% to 3%.	[103]
Chip on board (COB) packaging module with microlens array (MLA) of silicon has been used as the primary optics design	The light extraction efficiency (LEE) has been increased by 8% compared to the without MLA.	[104]
Spin on glass (SOG) MLA primary optics in circular shapes of different diameters	The LEE has been increased by 21.86% when using the 50 µm diameter.	[105]
Embedding The air gap between the LED chip and substrate by 4 wt% graphene oxide (GO)-based silicon composite	The junction temperature and internal thermal resistance have been reduced by 2.9 °C, and 34% respectively.	[106]
NUV LED Sapphire substrate modification by ultra-thin air cavity nanopatterned	The LEE has been increased by two fold compared to the flat sapphire substrate.	[107]