In this thesis, we have demonstrated several electronic and optoelectronic devices using low-dimensional materials - both two-dimensional and one-dimensional materials. In summary,
We demonstrated a nanowire-based junctionless transistor. We use h-BN, a two-dimensional insulator, as the gate dielectric. The combination of the unique material properties and the device architecture helped us fabricate p-type transistors with high field-effect mobility, high on current and excellent on-off ratio.
We designed and demonstrated an electrically defined self-aligned heterostructure device using partially overlapping gates. The device can be operated as an n-type and p-type transistor by applying appropriate gate biases. The device structure can be utilized as a test platform to discern the properties of the heterojunction without confounding the effects of contact resistance. This device can be operated as a tunnel transistor as well. At room temperature, we successfully demonstrated a sub 60 mV/dec subthreshold swing.
We fabricated a vertically integrated double-channel transistor based on ultrathin 2D material. The device structure effectively reduces the contact resistance, has good electrostatic integrity, and has a low device footprint. We demonstrated a high on current using this device.
Finally, we demonstrated an infra-red detection using stable wide-bandgap material heterostructure and electron transition from one material’s conduction band to the other’s conduction band. We analyzed multiple device architectures to understand the mechanism of the device operation from their bias-dependent photo response and simple physical models. The device exhibits good responsivity, broadband photoresponse, and good speed of operation.
Based on the devices discussed in this thesis, many possibilities are open for further improvement. Some are discussed below.
Further characterization and exploration of Tellurium nanowire transistors can be performed. The top priority among these would be to fabricate and characterize short-channel transistors. From a synthesis and fabrication point of view, techniques to fabricate useful circuits can be explored. Further, the optical properties of tellurium nanowires can also be studied.
The reconfigurable heterojunction can be used to develop useful. Further improvement of the device, especially in the tunnelling mode, can be useful for low-power circuits.
The dual-channel device can be experimentally validated for short-channel performance. A standard fabrication flow can be developed to make short-channel devices.
Some more device architectures and wide-band materials can be tested to improve the IR detector’s performance. Light absorption needs to be improved by engineering the proper geometry of the device. Characterization for higher wavelengths and achieving higher speed of operation can also be explored. Waveguide integration would also help to improve the light absorption in the detector.