Ali Javey (Advisor)

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...

So far, extensive research has been carried out for III-V semiconductor materials from crystal growth to device fabrications. The reason for this is that III-V shows the highest energy conversion efficiency due to high absorption coefficient and optimal and direct band gap. However, there is problem for III-V applications, which is the high cost of raw materials. We are exploring a method which addresses this limitation. High optical quality crystals have been grown on selected tiny areas to make array of crystals such as on metal foils. This should be useful as a PV without any loss...

The intrinsic advantages of III-V semiconductors for solar cells have been hobbled by the lack of low-cost substrates and processes, which has thus far limited market success of III-V solar cells. Here at Berkeley we are exploring a non-traditional approach which addresses these drawbacks. High optical quality polycrystalline InP films have been grown on non-epitaxial molybdenum substrates. Remarkably, these films with micron-sized grains have similar photoluminescence qualities as single- crystalline InP, and show great promise for high-efficiency, low-cost solar cells....

Efficient carrier selective contacts are key to electronic devices based on silicon including sensors, microelectromechanical systems, field effect transistors and photovoltaics. We explore substoichiometric molybdenum trioxide (MoOx, x<3) as a dopant-free, hole-selective contact for silicon. As a proof of principle, we demonstrate a silicon solar cell with a MoOx hole contact delivering a high open-circuit voltage of 711 mV and a power conversion efficiency of 18.8%. Due to the wide band gap of MoOx, we observe a substantial gain in photocurrent of 1.9 mA/cm2 in the ultraviolet...