InAs-based nanowires on silicon platform for novel nanoscale high electron mobility heterojunction devices

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Central objective of this project is the realization of advanced InAs nanowire (NW)-based high electron mobility devices fabricated by catalyst-free, site-selective molecular beam epitaxy, with a focus on vertical surround gate (VSG) tunnel-junction field effect transistors (TJ-NWFET) on silicon. Two complementary directions will be targeted: (a) microstructure-electrical transport property correla-tions in back-gated InAs NWFETs to identify the role of structural defects, distinct crystal phases and dopants, and set the base for optimized NW structures implemented into (b) high-performance InAs VSG-TJ-NWFETs, including core-shell high electron mobility transistor (HEMT) devices. The micro-structure-electrical transport studies will be conducted via gated 2-(4)-terminal current-voltage (I-V) measurements (temperature- and electric field-dependent), as well as by spatially resolved electrical scanning probe microscopy techniques. For the VSG-TJ-NWFET architectures on Si large emphasis will be on carrier transport across the InAs-Si tunnel junction (inter-band tunneling characteristics, negative differential resistance, etc.) controlled by band tuning mainly via doping, and investigated in reverse and forward bias conditions to derive the characteristic junction quality properties. Further-more, undoped and modulation-doped In(Ga,Al)As-InAs core-shell HEMT structures are designed for enhanced carrier confinement inside the NW core and suppression of surface scattering. These structures will be studied by the full spectrum of materials characterization methods, as well as theoretical model calculations of electronic transport of confined charge carriers in 1D/2DEG core-shell NW systems. This project may not only provide interesting insights into the performance of not yet investigated MBE-grown InAs NWFETs, but may open up also new directions for future development of InAs NW-based diode applications, such as photovoltaic and photodetection devices.