Novel nanowire integration schemes for massively parallel and manufacturable nanoscale electronics and photonics

In the last decade, the nanotechnology has made significant progress in the synthesis and demonstration of novel devices with semiconductor nanowires. However, interfacing and integrating nanowires in devices and circuits has remained a formidable challenge since they were first envisioned as building blocks of future electronics, photonics and sensing systems. We demonstrated an epitaxial bridging technique for interfacing nanowires that allows individual electrical access to a large number of nanowire devices without recourse to nanoprobes or tedious and expensive serial interfacing procedures. Two opposing electrically isolated semiconductor surfaces are fabricated using coarse optical lithography, along with wet and dry etching. Lateral nanowires are then grown from one surface and epitaxially connected to the other, forming electrically continuous and robust “nano-bridges”. By forming the structure on a silicon-on-insulator (SOI) substrate, electrical isolation is achieved. The nanowire devices fabricated using the bridging interfacing technique exhibit more than two orders of magnitude lower contact resistance and three orders of magnitude lower noise level than any other reported works. We extended our nano-bridging method and demonstrated heterogeneous bridged InP nanowires between Si surfaces. Interesting properties such as space charge limited current and a discernable level of persistent photocurrent were observed. The nano-bridging technique was expanded to fabricate high performance nanowire device on any type of substrates such as amorphous materials or even metals. Based on this new approach, a semiconductor nano-bridge based photodetector was designed and fabricated on a quartz substrate and an impressive bandwidth ≫30GHz was measured. These results demonstrate that it is now possible to design and manufacture nanowire based semiconductor devices without using expensive single crystal substrates. Exciting opportunities for novel high performance electronics and photonics on ultra-low cost surfaces such as quartz, plastic, FR4, metal etc. are likely to becoming a commercial realty.