Heterogeneous integration of CdS filters with GaN LEDs for fluorescence detection microsystems

J. Alex Chediak, University of California, Berkeley
Zhongsheng Luo, University of California, Berkeley
Jeonggi Seo, University of California, Berkeley
Nathan Cheung, University of California, Berkeley
Luke P. Lee, University of California, Berkeley
Timothy D. Sands, Birck Nanotechology Center; School of Materials Engineering; Electrical and Computer Engineering; Purdue University

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Microassembly of a hybrid fluorescence detection microsystem by heterogeneous integration of a CdS thin-film filter, an (In, Ga)N thin-film blue LED, and a disposable PDMS microfluidic device onto a Si PIN photodetector substrate is described. The CdS thin film filter was deposited directly onto a photodetector by pulsed-laser deposition. A thin-film (In, Ga)N LED was then transferred by a novel “pixel-to-point” laser lift-off process from the sapphire growth substrate to the silicon photodetector substrate. The final integration step was achieved by positioning a disposable polymer microfludic device onto the excitation/detection subsystem. Pixel-to-point transfer is potentially an enabling microassembly process for the fabrication of multicolor fluorescence-based bioassays and chemical detection microsystems.