Ali Javey (Advisor)

Research Advised by Professor Ali Javey

Javey Group:  List of Projects | List of Researchers

BPN465: Conformal Ultra-shallow Junction Formation for 3-D Structured InP Nanopillar Solar Cell

Kee Cho
Onur Ergen
Rehan Kapadia
2011

Solar energy represents one of the most abundant and yet least harvested source of renewable energy. We report a PV structure that incorporates 3D, single crystalline n-CdS nanopillars, embedded in poly- crystalline thin films of p-CdTe, to enable high absorption of light and efficient collection of the carriers. Through experiments and modeling, we demonstrate the potency of this approach for enabling highly versatile solar modules on both rigid and flexible substrates with enhanced carrier collection efficiency arising from the geometric configuration of the NPLs. We performed...

BPN647: Ultra-Thin Body, Mixed Anion Arsenide-Antimonide XOI FETs

Hui Fang
Steven Chuang
Kuniharu Takei
2011

We demonstrate ultrathin body (UTB) high mobility InAsSb-on-insulator (XOI) n-FETs. The devices are obtained by the epitaxial layer transfer (ELT) of ultrathin InAsSb layers (thickness, 7-17 nm) onto Si/SiO2 substrates. InAsSb XOI FETs exhibit a peak effective mobility of ~5000 cm2/V-s and an ION/IOFF ratio of over 104. The top-gated devices exhibit an impressive ION of ~0.24 mA/micron (LG~500 nm) at VDD=0.5 V and a SS of ~109 mV/dec. These results demonstrate the utility of the XOI platform for obtaining high mobility n-FETs on Si by using mixed anion arsenide-antimonide as the...

BPN635: Structured Substrates for Enhancing the Water-Splitting Efficiency of Earth Abundant Materials

Maxwell Zheng
2011

Here we focus on nano- and micro-structuring earth abundant materials to improve their water splitting performance, primarily by increasing the optical path length. The focus is on isolating structural effects and so we fix the material system to be titanium dioxide. In one structure we use texturized carbon nanotubes as the back contact. In another, we are planning to use micro-scale triangular grooves.

Project end date: 02/06/12

BPN640: p-InP nanopillars for highly efficient water splitting

Min Hyung Lee
2011

The photoelectrochemical evolution of hydrogen using p-InP nanopillar arrays decorated with metallic co-catalyst is explored. The nanopillar devices exhibit an great enhancement in the conversion efficiency, as compared to planar substrates. This behavior is mainly attributed to the low surface reflectivity of nanopillar arrays along with the enhanced surface area for catalytic reactions. Of particular importance to this architecture is the use of InP as the absorber layer, which is known to have a low carrier surface recombination velocity, thereby minimizing the loss of...

BPN641: InAs XOI Gas Sensor

Junghyo Nah
2011

The objective of InAs XOI gas sensor project is twofold. First, the role of size effect on sensor performance will be systematically investigated. Our XOI device structure provides a unique platform to perform this study since we can precisely control material thicknesses and transfer them on a SiO2/Si substrate. Based on this study, we will determine physical role of size effect on sensor performance. This result will be also essential to determine an optimum NR thickness for gas sensors. Secondly, we will implement multiple gas detection sensor modules on a single chip by...

BPN567: Compound Semiconductor on Insulator (XOI) FETs

Rehan R. Kapadia
Kuniharu Takei
Hui Fang
Steven Chuang
2012

Due to their high mobility, the integration of compound semiconductors on Si has been actively studied over the past several years. This integration, however, presents significant challenges. The conventional method of addressing this problem consists of growth of multiple epilayers of materials to address the lattice mismatch between Si and the desired semiconductor, leading to highly complex fabrication techniques. Here we demonstrate high performance compound semiconductor on insulator (XOI) field effect transistors (FET) consisting of ultra-thin InAs nanoribbons (NR) on insulator...

BPN667: Optical Absorption Study of 2-Dimensional III-Vs

Hui Fang
Kuniharu Takei
2012

Recently, a new type of 2-D material, free standing InAs nanomembranes (thickness of 3 - 19 nm), as a representative of III-V semiconductors, was realized by layer transfer and this enables optical studies of 2-D InAs which were previously inaccessible, by decoupling those ultra-thin layers from original growth substrates to any optically transparent substrates. By using Fourier Transform Infrared (FTIR) spectroscopy, we directly observe the optical transitions from 2-D subbands, with energy spacing in line with the particle in the box model. Furthermore, it is found that the...

BPN533: Nanomaterial-Based Artificial Skin Sensor

Kuniharu Takei
Toshitake Takahashi
Chuan Wang
2012

Flexible large-scale devices are of great interest for wearable human interface applications. We have developed a technique of "uniform nanomaterial patterning" for the integration of high- performance inorganic nanomaterials on user-defined substrates. This project is to realize large scale flexible multi-functional electronics by utilizing nanomaterials such as nanowires, nanotubes, and nanoparticles. As one of applications, we here demonstrate mechanically flexible large scale high sensitive multi-functional artificial skin by proposing different types of sensors such as a...

BPN469: Ultra-Short Channel 1D-2D Compound Semiconductor on Insulator (XOI) FETs

Steven Chuang
Kuniharu Takei
2013

Recently, compound semiconductor on insulator(XOI)has risen as a promising platform for next generation high performance electronics, as it inherits advantages from both SOI and high mobility III-V materials. In order to test the performance limit of this platform, we plan on fabricating ultra-short channel XOI FETs. This project will involve various controlled experiments to better understand the underlying physics of XOI FETs, thus allowing us to progress towards the ultimate XOI FET.

Project end date: 08/16/13

BPN659: High Performance Flexible Integrated Circuits Using Carbon Nanotube Networks

Chuan Wang
Kuniharu Takei
Toshitake Takahashi
2013

In this Project, we report the use of high-purity semiconducting carbon nanotube networks and 2-dimensional III-V nanomembranes for high-performance integrated circuits on mechanically flexible substrates for digital, analog, and radio-frequency applications. We have demonstrated high-performance carbon nanotube thin-film transistors (TFTs) with on-current, transconductance, and field-effect mobility up to 15 uA/um, 4 uS/um, and 50 cm2/Vs. Using such devices, digital logic gates with superior bending stability have been demonstrated. We have also employed a self-aligned device...