PSS (patterned sapphire substrate) technology
In order to produce more efficient LEDs, manufacturers have developed patterned sapphire substrate (PSS) technology.
A sapphire substrate (sapphire wafer) can be easily patterned using nanoimprint as it does not require a precise alignment between the mold and the substrate.
Moreover, nanoimprint on a sapphire substrate can be done at a very reasonable cost if compared with optical lithography or other techniques. The main advantage of patterned sapphire wafers is that surface patterning helps extract more light therefore improving the LED substrate efficiency.
A big issue with polished sapphire substrates is that most part of the light produced goes back into the LED.
By using a patterned sapphire wafer, more light gets extracted therefore improving the LED substrate efficiency: with patterned sapphire substrates, the efficiency can be improved by as much as a third if compared with non-patterned sapphire LEDs.
Patterning of the substrate can be done via usual patterning techniques and etching.
There is another relevant improvement with the use of patterned sapphire LEDs: the nano-patterned sapphire layer has a positive effect on the semiconductor growth process as it allows the growth of the GaN layer in parallel to the surface plane and helps reduce the number of dislocations that degrade performance.
Martini Tech is proud to offer our own sapphire substrate technology for patterning test wafers of various sizes.
Most patterns today are based on proprietary design from LED manufacturers.
It is essential for LED manufacturers to select the right pattern to be used in order to achieve the highest efficiency possible.
Patterns may vary from cones to pyramids and flat tops and can be organized in hexagonal or trigonal arrays.
Martini Tech offers a sapphire substrate patterning service where the user can select the pattern of his/her choice.
Good quality of NIL master mold and a robust imprint process mean that the pattern is faithfully replicated on the sapphire substrate and this leads to a higher LED efficiency .
Martini Tech offers a full range of services for testing new sapphire substrate patterns.
Please feel free to contact us for further information.