Hsi-Jen J. Yeh

Fluidic self-assembly for the integration of GaAs light-emitting diodes on Si substrates

The integration of GaAs optoelectronic devices on Si VLSI is important for many high-bandwidth communication applications. In this paper we describe a novel technique for the quasi-monolithic integration of GaAs light-emitting diodes on Si substrates that utilizes fluid transport and shape differentiation for placement and orientation. GaAs light-emitting diodes fabricated into trapezoidal blocks are suspended in a carrier fluid and deposited over holes etched in Si for integration. Top-side ring contact and bottom electrical contact are fabricated on the blocks prior to integration.<<ETX>>

Fluidic self-assembly of microstructures and its application to the integration of GaAs on Si

A new technique for the self-assembly of microstructures is demonstrated in this paper. Freed microstructures suspended in a fluid are assembled onto a host substrate by fluidic transport. The microstructures are fabricated with specific binding features. They are freed from their original substrate by sacrificial etching and transferred into an inert carrier fluid. Before the microstructures are freed, they can also be bonded to an intermediate substrate where their original-substrate is removed. This provides access to the other side of the microstructures for processing before they are freed into the carrier fluid. The fluid is then dispensed onto a host substrate with specific features to control the positioning and the orientation of the microstructures. In this way an abundance of microstructures can be made in advance and assembled onto the substrates as desired. This is especially advantageous for the integration of microstructures and substrates made of incompatible material systems, e.g. GaAs on Si. Microstructures can be fabricated densely packed on the substrate prior to freeing, and the fluid containing them can be recycled to minimize waste. Also, different types of devices can be simultaneously placed at different positions on the host substrates by using selective features that differentiate among devices features.

Fluidic self-assembly of silicon microstructures

Fluidic self-assembly is a new technique which makes possible the integration of devices fabricated using dissimilar materials and processes. The integration is accomplished by fluidically transporting trapezoidally shaped blocks made of one material into similarly shaped holes in a receptor substrate. In this paper, a systematic study of the FSA integration efficiency is presented. Blocks and holes were formed from silicon using anisotropic etching. Two different sizes were considered: large blocks of dimension 1.0 mm/spl times/1.2 mm, and small blocks of dimension 150 /spl mu/m/spl times/150 /spl mu/m. FSA was performed in either water or methanol using a bubble pump apparatus to recirculate blocks. FSA of large blocks resulted in 100% filling of a substrate containing 191 holes within 2.5 minutes. Similar experiments with small blocks and a substrate with a 64/spl times/64 array of holes yielded a fill ratio of 70%, due to undesirable adhesion of blocks to the substrate surface. Roughening the substrate resulted in a fill ratio of 90%. Also presented is a simple rate equation model of the FSA process, along with a discussion of which process parameters are important and how they can be optimized.

Integration of GaAs vertical‐cavity surface emitting laser on Si by substrate removal

Substrate removal techniques are attractive for the integration of III‐V compound semiconductor devices on Si for the integration of optical and electronic devices, and on thermally conducting substrates for heat sinking. Here we discuss the bonding of strained quantum well InGaAs vertical‐cavity surface‐emitting lasers on both Si and Cu substrates. The GaAs substrates are then removed by selective etching. Lasing was achieved with pulsed electrical pumping with Jth=2.5 kA/cm2. The performance characteristics of the Si and Cu bonded devices are compared.