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We have analyzed and modeled the reverse-biased gate leakage current in a Schottky-gate AlGaN/GaN high electron mobility transistor. While the Poole–Frenkel emission current along conductive threading dislocations dominates at low negative gate bias, the trap-assisted tunneling of thermally energized electrons and the thermal emission of electrons from threading dislocations aided by dislocation-related states at multiple energy levels within the AlGaN bandgap are dominant at moderate to large reverse bias. Additionally, deep trap levels of high density localized near the gate/AlGaN interface cause significant leakage at 473 K at low to moderate reverse bias, which could be specific to the device we have analyzed. We extracted about 10 12 cm − 2 traps near the AlGaN/GaN interface from the difference of the barrier layer electric field profile obtained from the experimental high-frequency capacitance–gate voltage and the one needed for final matching. The thermionic- and the thermionic field-emission currents are considerably low; the latter, however, dominates in the defect-free case. Finally, the simulation framework we developed here helped us identify various conduction mechanisms contributing to the reverse-biased gate leakage and the density and electronic structure of the responsible defects. [ABSTRACT FROM AUTHOR]

The present paper seeks to focus on one of the prominent aspects of South Asian comics; the nature of urbanity, through a study of Sarnath Banerjee's All Quiet in Vikaspuri, a narrative primarily set in Delhi. Banerjee's Delhi is the space of the capitalists, urban planners, and corrupt policies; in short a 'social product', as Henri Lefebvre had formulated. The paper will examine how Delhi, in Banerjee's comics, is symptomatic of various states of discriminatory infrastructural development, failure and violence endemic to the system, as in many other emerging South Asian cities. It will further investigate the dynamics of uneven development and urban inequality of Delhi to argue the emergence of new socio-spatial and economic trajectories in post-liberalisation India. The paper seeks to argue that through the multiple references to pulp fictions, mythic and hybrid spaces, Banerjee maps the nuanced changes in urban lifestyle and the more liberal shift towards exclusionary spatial practices such as 'short-termism', but also present alternative histories and regional resistance of the lived space that go against the planned space of the city. Finally, the paper will borrow insights from theorists such as Sanjay Srivastava, Ananya Roy, David Harvey, and others to argue how social and spatial justice can be achieved through urban comics that, according to Dominic Davies, helps to restructure 'more socially and spatially just cities'. [ABSTRACT FROM AUTHOR]

In this interview, Ritam Sarkar and Somdatta Bhattacharya talk to the French comics artist Simon Lamouret, to discuss his comics The Alcazar. Lamouret is a graphic novelist and illustrator based out of Toulouse, France. He has produced two graphic novels: Bangalore (part of the Angouleme International Comics Festival selection) and L'Alcazar (Winner of the debut award ADAGP/Quai des Bulles, France, 2021). L'Alcazar was published in India in 2022 as The Alcazar. In this conversation, Lamouret talks about his creative process, his experiences of living in Bangalore and the relationship comics share with cities. The interview was conducted on 3 July 2022 via Microsoft Teams. It has been edited for length and clarity. [ABSTRACT FROM AUTHOR]

In this article, we report the temperature-dependent transistor characteristic of Epi-Gd2O3/AlGaN/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT) and compare its properties with that of AlGaN/GaN metal-Schottky high electron mobility transistor (HEMT) grown on 150 mm Si (111) substrate. Introducing an epitaxial single crystalline Gd2O3 between the metal gate and AlGaN barrier not only improves the gate leakage current significantly but also enhances its thermal stability. We observe that there is no significant change in the gate leakage current even at 473 K compared to that measured at room temperature (RT) (298 K), and this is also evident in the transistor’s subthreshold behavior at 473 K. We have determined the electric field within the Gd2O3 as well as AlGaN and investigated the leakage conduction mechanism through Gd2O3. The ION/IOFF of the transistor was measured as high as ~108 even at 473 K with the lowest VTH shift (91.4 mV) with temperature. Our measurements also confirm the presence of polar optical phonon scattering, which directly affects the 2-D electron gas (2DEG) mobility at high temperatures and thus the electrical characteristics of HEMT and MOSHEMT. [ABSTRACT FROM AUTHOR]

In this letter, we report the impact of epitaxial Gd2O3 on the electrical properties of an AlGaN/GaN high electron mobility transistor (HEMT) grown on a 150 mm diameter Si (111) substrate. Incorporation of epitaxial Gd2O3 grown by the molecular beam epitaxy technique under a metal gate (metal/Gd2O3/AlGaN/GaN) causes six orders of magnitude reduction in gate leakage current compared to metal/AlGaN/GaN HEMT. We observe that epi-Gd2O3 undergoes complete structural changes from hexagonal to monoclinic as the thickness of the layer is increased from 2.8 nm to 15 nm. Such structural transformation is found to have a strong impact on electrical properties whereby the gate leakage current reaches its minimum value when the oxide thickness is 2.8 nm. We find a similar trend in the density of interface traps (Dit) having a minimum value of 2.98 × 1012 cm−2 eV−1 for the epioxide layer of thickness 2.8 nm. Our measurements also confirm a significant increase in the two dimensional electron gas (2DEG) density (∼40%) at AlGaN/GaN interface with epioxide grown on AlGaN, thus confirming the contribution of epitaxial lattice strain on 2DEG modulation. [ABSTRACT FROM AUTHOR]

We have investigated the effect of nitridation time of the sapphire substrates on the structural, morphological, optical, and electrical characteristics of InN thin films grown by plasma assisted molecular beam epitaxy technique. Three sets of the films were prepared with nitridation times of 1, 2.5 and 3 h, respectively. Full width at half maximum (FWHM) of ω-scans around X-ray diffraction peaks of different symmetric and asymmetric planes were drastically reduced with increasing nitridation time, hence the threading dislocation densities were also reduced by order of magnitude (2.4 × 1011 cm−2 to 6.7 × 1010 cm−2). The atomic force microscopy also showed improvement in surface roughness. But interestingly, on increasing the nitridation time, a prominent blue shift in the photoluminescence (PL) spectra (~ 60 meV) was observed which has also been confirmed by infrared absorption spectroscopy (blue shift of ~ 120 meV). This phenomenon of blue shift of PL peak was attributed to increase in electron concentration (n) in InN layer and was further confirmed by the Hall measurement. Carrier concentration (n) is seen to increase from 6.8 × 1018 cm−3 to 1.8 × 1019 cm−3 while the highest mobility was estimated to be 164 cm2/V-s which is observed to decrease considerably upon longer nitridation time. Thus there is a trade-off between structural and electrical qualities of InN film upon prolonged nitridation. [ABSTRACT FROM AUTHOR]

Three sets of InGaN/GaN nanowire (NW) heterostructures are grown on Si(111) substrates under different growth conditions. A quasi‐two‐dimensional p‐GaN layer is grown on top of those structures using the epitaxial lateral overgrowth (ELOG) technique. Finally, the light‐emitting diodes (LED) are fabricated using these hybrid nanostructures following standard fabrication techniques. Electroluminescence (EL) measurement confirmed the emission wavelengths of 530.0 nm (green), 608.3 nm (orange), and 632.5 nm (red). The knee voltages of the devices are estimated to be in the range of 2.18–2.89 V, with higher knee voltages for samples emitting lower wavelengths. Further analysis of forward bias electrical characteristics suggests the dominance of tunneling current and an increase in the defect density in the heterostructures emitting higher wavelengths. [ABSTRACT FROM AUTHOR]

We have demonstrated the growth of high-quality Al x Ga (1-x) N (x ∼ 50%) nanowires (NWs) for the first time on the sapphire substrate without using GaN NWs as the template, by plasma-assisted molecular beam epitaxy. Our newly developed process elucidates that depending on the substrate temperature and V/III ratio an AlGaN network is formed on sapphire substrate prior to the NWs growth. We find that the ledges of this kinked shaped network act as nucleation sites for the NW growth. The present observations suggest that availability of nucleation sites and higher substrate temperature during growth are the key parameters for the growth of homogeneous AlGaN NWs on the sapphire substrates. Energy dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, Raman spectroscopy, x-ray diffraction, photoluminescence spectroscopy, and scanning electron microscopy analysis show that AlGaN NWs exhibit near-atomic scale compositional uniformity along the length as well as across the diameter.