MML capabilities for fabrication and electrical/ optical testing of semiconductor nanowire & thin film structures include: 1) two newly built chemical vapor deposition (CVD) reactors for Group III nitrides (GaN, AlN, InN and their alloys) and Si/Ge materials; 2) a measurement platform for electrical and optical characterization of nanowires and thin films.
The CVD reactors (see nitride reactor in Fig. 1) are suitable for fabricating semiconductor nanowires and thin films on the user'S substrate of choice, dimensions up to 2 inch diameter, with growth capabilities that enable controlled crystalline growth direction, crystallographic orientation, nanowire size and properties through: growth rates from as low as ~ 1 nm/S to as high as ~20 nm/S; substrate that can be rapidly transferred to/from the growth zone to interrupt/resume growth as required to make heterostructures with sharp interfaces; doping capabilities including with metals and nonmetal electrically-active and magnetic elements; much lower carbon contamination than metalorganic CVD systems.
The measurement platform includes 4-probe electrical testing, UV-visible detection and microwave guides for specimen testing in an environmental chamber having controlled atmosphere, pressure, temperature, and magnetic field.
The CVD growth systems enable in-house fabrication of semiconductor nanomaterials that are not available externally. This source of nanowire & thin film test structures, yielding well-defined structural, electrical and optical characteristics, is enabling development of nanoscale metrology tools such as active-tip Near-Field Scanning Optical Microscopy elements and innovative technologies including nanophotonics, electronics and sensors.
The combination of nanowire fabrication and electrical/optical measurement tools led to recent demonstration of two key nanowire device structures: GaN NW based field-effect-transistor (NWFET) and a NW light-emitting diode (LED).