LED manufacturing issues concerning gallium nitride-on-silicon (GaN-on-Si) technology and wafer scale up challenges

Abstract

We demonstrated the growth of blue LED structures grown on 4-inch and 8-inch Si (111) substrates. GaN layers that have low threading dislocation density (TDD) of 1.6×10 8 /cm 2 , which is comparable to state of the art in GaN on sapphire, can be obtained on 4inch Si substrate by using a new TDD reduction technology using a silicon nitride (SiN) interlayer. A dependence of LED device performance on threading dislocation density was studied by using 4-inch Si substrate. A LED manufacturing technology has been developed by using 8-inch Si towards mass production technology. The light output power representing a median performance exceeded 641 mW at 350 mA, which was comparable to state-of-the-art LED.

Demonstration of novel high-efficiency blue LEDs on silicon substrates

“…5 In addition, we have previously developed LEDs with low threading dislocation densities (TDDs), i.e., of less than 2 10 8 cm 2 on Si (111 crystallographic plane) substrates. 6,7 Those TDD values were almost the same as those of LEDs grown on Al 2 O 3 (0001) substrates. We achieved this reduction of TDDs by using multiple modulations of dislocations during the formation of GaN islands on a silicon nitride (SiN) interlayer, and from the growth of the SiN cap layers on the GaN island surfaces.…”

“…We have previously provided a detailed description of the AlGaN buffer layer structure and the properties of the i-GaN layer. 6,7 In the next step of our process, an n-GaN (i.e., n-type) layer, MQW active layers, and p-type layers were grown sequentially. Our target layer structures for the MQWs were those shown in Figure 1.…”

Porous Nitride Light-Emitting Diodes

“…The total epitaxial thickness is 1.1 μm, which is much thinner than the 3.5−5.0 μm typically requested for highefficiency blue LEDs on Si substrates. 10,12 Indeed, decreasing the total thickness of the structure can be an asset in order to decrease the total growth time. The purpose of the n-AlGaN below the SL is to act as a sublimation stop layer; however, we will see in the following that locally, the selective area sublimation process used to porosify the sample can go through this layer, probably due to an insufficiently high Al composition.…”

The efficiency challenge of nitride light‐emitting diodes for lighting

“…To ensure high extraction efficiency, substrate removal is required, but this is anyway the case for a number of GaN or sapphire laser lift‐off, flip‐chip approaches. With this approach remarkable results have been recently obtained with GaN on Si .…”