Mahesh Gokhale

Magnetotransport properties of individual InAs nanowires

We probe the magnetotransport properties of individual InAs nanowires in a field effect transistor geometry. In the low magnetic field regime we observe magnetoresistance that is well described by the weak localization (WL) description in diffusive conductors. The weak localization correction is modified to weak anti-localization (WAL) as the gate voltage is increased. We show that the gate voltage can be used to tune the phase coherence length (

Tunable thermal conductivity in defect engineered nanowires at low temperatures

l_phi

Wide bandwidth nanowire electromechanics on insulating substrates at room temperature.

) and spin-orbit length (

Understanding the effect of nanowire orientation on time evolution of Raman spectra from laser irradiated InAs nanowire surface

l_{so}

Optoelectronic devices based on III-N quantum wells grown on CVD graphene

) by a factor of

Time-resolved THz-spectroscopy of InAs nano-wires

sim

THz spectroscopy of InAs nanowires

2. In the high field and low temperature regime we observe the mobility of devices can be modified significantly as a function of magnetic field. We argue that the role of skipping orbits and the nature of surface scattering is essential in understanding high field magnetotransport in nanowires.

Study of the microstructure in MOVPE grown InN epitaxial layers by high resolution x-ray diffraction

We measure the thermal conductivity (κ) of individual InAs nanowires (NWs), and find that it is three orders of magnitude smaller than the bulk value in the temperature range of 10–50 K. We argue that the low κ arises from the scattering of phonons in the random superlattice of twin defects oriented perpendicular to the axis of the NW. We observe a significant electronic contribution arising from the surface accumulation layer, which gives rise to the tunability of κ with the application of an electrostatic gate and a magnetic field. Our devices and measurements of κ at different carrier concentrations and magnetic field offer a means to study unique aspects of nanoscale thermal transport.

Two Distinct Origins of Highly Localized Luminescent Centers within InGaN/GaN Quantum‐Well Light‐Emitting Diodes

We study InAs nanowire resonators fabricated on sapphire substrate with a local gate configuration. The key advantage of using an insulating sapphire substrate is that it results in a reduced parasitic capacitance, thus allowing both wide bandwidth actuation and detection using a network analyzer as well as signal detection at room temperature. Both in-plane and out-of-plane vibrational modes of the nanowire can be driven and the nonlinear response of the resonators studied. In addition, this technique enables the study of variation of thermal strains due to heating in nanostructures.

Microstructure of InN epilayers deposited in a close-coupled showerhead reactor

We investigate differences observed in the time evolution of Raman spectra for differently oriented (in plane) InAs nanowires (NWs), using polarized Raman spectroscopy. Specially designed polarized Raman spectroscopy experiments elucidate that laser irradiation leads to the formation of an oriented crystalline oxide film on the InAs NW surface. Both the formation of oriented crystalline oxides and Raman selection rules leading to the presence/absence of oxide peaks in the unpolarized Raman spectra are uncommon occurrences and can lead to incorrect interpretations of the oxidation process, if not looked into carefully. Further, the specially designed heating and cooling experiments for a mixed phase (wurtzitexa0+xa0zinc blende) InAs NW revealed the formation of specific allotropes of elemental As, i.e. gray-As (rhombohedral) and black-As (orthorhombic: metastable) at low (700-950 K) and high simulated temperatures (1000-1300 K) on the InAs NW surface, respectively. Both have high electrical conductivity due to a layered structure and control over the growth of only a few layers using laser irradiation envisages properties similar to graphene. This kind of surface of InAs NWs has the potential for novel device applications, where a semiconductor-insulator-metal heterostructure is required.