industry  interview


Figure 7a: Right) 1mm, GaN-on-silicon chips are capable of


producing cool- white LEDs with a flux of 110 µm. Figure 7b: (Far right) External quantum efficiency vs. current


Performance of 1mm chip


100 200 300 400 500 600 700 800 900 1000


0 0 200 400 600 DC drive current (mA) 10


Light output (mW) Vf (V)


0 1 2 3 4 5 6 7 8 9


800


80% 70% 60% 50% 40% 30% 20% 10% 0%


0.01


EQE curve of 1x1mm chip


0.1


J/A*cm-2 1


10


100


refinement and better control, silicon-based products are now finding more and more applications and customers.


Due to the vertical thin-film structure, silicon-based devices can be made smaller than similar performance equivalents based on sapphire. 200 µm by 200 µm devices for display application are in high demand, and they now have proven long-term reliability. What’s more, the production yield can be on a par with its sapphire sisters currently in use.


To put it simply, the GaN-on-silicon LED is no different from any sapphire or SiC-based LEDs. Its application ranges from displays, backlighting and general lighting. Figure 9 is a full color display featuring our GaN-on-silicon blue and green LEDs. In this particular application, the chip size is 170 µm by 170 µm, and the blue output power is close to 10 mW at 20 mA.


Figure 9: A high- density LED full color display that features blue and green GaN LEDs grown on silicon substrates


Our current 2-inch GaN-on-silicon process has proved that it is possible to mass-produce this class of device, which combines high performance with high quality and high reliability. The real benefit for GaN on silicon will only be realized at far larger diameters, such as 6 inches and above. This will lead to higher capacity and utilization of standard IC processing tools and equipments, but getting there will require overcoming issues related to these large diameter platforms.


 Contributors for this article from Lattice Power Corporation are Jiang Fengyi, Wangli, Wang Xiaolan, Fang Wenqing , Mo Chunlan , Liu Junlin, Tang Yingwen, Xiong Chuanbing, Cheng Haiying, Zheng Changda, Zhou Yinghua, Yan Zhanbiao, and Bo Lu (blu@latticepower.com).


FURTHER READING ICNS-8, Session H: Epitaxial Growth I, L_1006: “High power InGaN LEDs grown on Si substrate by MOCVD”, October 18- 23, 2009, ICC Jeju, Korea.


34 www.compoundsemiconductor.net June 2010


1.1 1.2


1.1 1.2


0.6 0.7 0.8 0.9 1


0.6 0.7 0.8 0.9 1


500um chip reliability data 500um chip reliability data


Test condition:


75C board temperature, 200mA drive current


0hr 24hr 72hr 240hr 576hr 1000hr Lifetest hrs


0hr 24hr 72hr 240hr 576hr 1000hr Lifetest hrs


1000um chip reliability data 1.2


0.2 0.4 0.6 0.8 1


0


0 200 400 600 800 1000 1200 life test hrs


Figure 8: reliable operation of GaN on silicon LED


SPIE OPTO: SPIE paper number 7617-48, “High-power GaN- based Blue LEDs grown on Si substrate by MOCVD” Optoelectronic Materials, Devices and Applications, 23-28 January 2010


Light output (mW)


LOP/LOP0


LOP/LOP0 LOP/LOP0


EQE


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