Fabrication of High Electrical Mobility Transistors on Flexible Substrates for Phased Array Radar and Terahertz Antennas

Compound semiconductor films are the key ingredient enabling the construction of ultrafast (>10 GHz) transistors. Materials such as Gallium Arsenide (GaAs), Gallium Nitride (GaN), Silicon Germanium (SiGe) and Indium Phosphide (InP) have shown great potential to enable a quantum leap in transistor performance. There are numerous commercial and military applications for such ultrafast transistors. A particularly challenging application area is for phased array radar and terahertz antenna fabrication. These devices require the construction of high frequency transistors on large (over 1 m2), flexible substrates in order to meet the demanding requirements for fast beam steering and high angular resolution for rapid target identification and tracking. In this STTR program, we propose to develop a new process technology for fabrication of high electrical mobility transistors (HEMTs) on flexible substrates. Commercial Kapton substrates with upper process temperatures of 300-450°C will be used to support low (< 500°C) temperature-deposited semiconductor films including Si, Ge, GaN, and InP. Sequential lateral solidification (SLS), an excimer laser crystallization process, will be performed in an appropriate background atmosphere to convert the as-deposited compound semiconductor films into low-defect-density microstructures, including large single-crystal regions. The resulting substrates will then be suitable for large-area patterning of HEMTs.