Alin Fecioru

Transfer-printing-based integration of single-mode waveguide-coupled III-V-on-silicon broadband light emitters

We present the first III-V opto-electronic components transfer printed on and coupled to a silicon photonic integrated circuit. Thin InP-based membranes are transferred to an SOI waveguide circuit, after which a single-spatial-mode broadband light source is fabricated. The process flow to create transfer print-ready coupons is discussed. Aqueous FeCl3 at 5°C was found to be the best release agent in combination with the photoresist anchoring structures that were used. A thin DVS-BCB layer provides a strong bond, accommodating the post-processing of the membranes. The resulting optically pumped LED has a 3 dB bandwidth of 130 nm, comparable to devices realized using a traditional die-to-wafer bonding method.

Transfer Printing of AlGaInAs/InP Etched Facet Lasers to Si Substrates

InP-etched facet ridge lasers emitting in the optical C-band are heterogeneously integrated on Si substrates by microtransfer printing for the first time. 500 μm × 60 μm laser coupons are fabricated with a highly dense pitch on the native InP substrate. The laser epitaxial structure contains a 1-μm-thick InGaAs sacrificial layer. A resist anchoring system is used to restrain the devices while they are released by selectively etching the InGaAs layer with FeCl3:H2O (1:2) at 8 °C. Efficient thermal sinking is achieved by evaporating Ti-Au on the Si target substrate and annealing the printed devices at 300 °C. This integration strategy is particularly relevant for lasers being butt coupled to polymer or silicon-on-insulator (SOI) waveguides.

Pressure activated interconnection of micro transfer printed components

Micro transfer printing and other forms of micro assembly deterministically produce heterogeneously integrated systems of miniaturized components on non-native substrates. Most micro assembled systems include electrical interconnections to the miniaturized components, typically accomplished by metal wires formed on the non-native substrate after the assembly operation. An alternative scheme establishing interconnections during the assembly operation is a cost-effective manufacturing method for producing heterogeneous microsystems, and facilitates the repair of integrated microsystems, such as displays, by ex post facto addition of components to correct defects after system-level tests. This letter describes pressure-concentrating conductor structures formed on silicon (1 0 0) wafers to establish connections to preexisting conductive traces on glass and plastic substrates during micro transfer printing with an elastomer stamp. The pressure concentrators penetrate a polymer layer to form the connection, and...

Miniaturized LEDs for flat-panel displays

Inorganic light emitting diodes (LEDs) serve as bright pixel-level emitters in displays, from indoor/outdoor video walls with pixel sizes ranging from one to thirty millimeters to micro displays with more than one thousand pixels per inch. Pixel sizes that fall between those ranges, roughly 50 to 500 microns, are some of the most commercially significant ones, including flat panel displays used in smart phones, tablets, and televisions. Flat panel displays that use inorganic LEDs as pixel level emitters (μILED displays) can offer levels of brightness, transparency, and functionality that are difficult to achieve with other flat panel technologies. Cost-effective production of μILED displays requires techniques for precisely arranging sparse arrays of extremely miniaturized devices on a panel substrate, such as transfer printing with an elastomer stamp. Here we present lab-scale demonstrations of transfer printed μILED displays and the processes used to make them. Demonstrations include passive matrix μILED displays that use conventional off-the shelf drive ASICs and active matrix μILED displays that use miniaturized pixel-level control circuits from CMOS wafers. We present a discussion of key considerations in the design and fabrication of highly miniaturized emitters for μILED displays.

Integration of GaN HEMTs onto Silicon CMOS by micro Transfer Printing

Integration of GaN high voltage transistors into Silicon CMOS could combine superior electrical parameters of GaN HEMTs and the huge logic functionality of Silicon CMOS. Several issues of a monolithic integration of GaN devices into CMOS like material mismatch and thermal budgets can be overcome by heterogeneous integration by micro Transfer Printing. Results of first printing experiments with small GaN on Si HEMTs are presented.

Heterogeneous Integration of Microscale Gallium Nitride Transistors by Micro-Transfer-Printing

Discrete gallium nitride high electron mobility transistors (HEMTs) are fabricated on oriented silicon, then undercut and assembled onto non-native silicon CMOS wafers by elastomer stamp micro-transfer-printing. The thin, less than 5 μm thick, gallium nitride transistors were then electrically interconnected using conventional thin-film metallization processes. Electrical measurements reveal that the heterogeneous integration process is benign to the underlying silicon transistors, and that the heterogeneous wide bandgap GaN transistors maintain their characteristic high voltage performance after being undercut and transferred to the non-native CMOS wafer.

Process Capability and Elastomer Stamp Lifetime in Micro Transfer Printing

Elastomer stamp based micro assembly or micro-transfer printing is a practical method for heterogeneous integration of micro-scale devices onto non-native substrates. In this paper, we evaluate the effect of stamp lifetime on performance and assess the useful lifetime of a stamp, both key metrics for using this technology in a manufacturing environment. We also review the performance of micro transfer-printing in several applications where >99% print yields and precise placement has been demonstrated.

Integration of a III-V light emitter on a silicon photonic IC through transfer printing

For the first time, III-V opto-electronic components are coupled to silicon waveguide circuits using transfer-printing. Efficient III-V material usage is enabled in silicon photonics by providing III-V only where needed. We present transfer-printed single-spatial-mode LEDs coupling to silicon-on-insulator waveguides as first examples of this technology.

AlGaAs ridge laser with 33% wall-plug efficiency at 100 °C based on a design of experiments approach

Upcoming applications for semiconductor lasers present limited thermal dissipation routes demanding the highest efficiency devices at high operating temperatures. This paper reports on a comprehensive design of experiment optimisation for the epitaxial layer structure of AlGaAs based 840 nm lasers for operation at high temperature (100 °C) using Technology Computer-Aided Design software. The waveguide thickness, Al content, doping level, and quantum well thickness were optimised. The resultant design was grown and the fabricated ridge waveguides were optimised for carrier injection and, at 100 °C, the lasers achieve a total power output of 28 mW at a current of 50 mA, a total slope efficiency 0.82 W A−1 with a corresponding wall-plug efficiency of 33%.