Heterostructures of III-Nitride Semiconductors for Optical and Electronic Applications

III-Nitride-based heterostructures are well suited for the fabrication of various optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), high-power/high-frequency field-effect transistors (FETs), and tandem solar cells because of their inherent properties. However, the heterostructures grown along polar direction are affected by the presence of internal electric field induced by the existence of intrinsic spontaneous and piezoelectric polarizations. The internal electric field is deleterious for optoelectronic devices as it causes a spatial separation of electron and hole wave functions in the quantum wells, which thereby decreases the emission efficiency. The growth of III-nitride heterostructures in nonpolar or semipolar directions is an alternative option to minimize the piezoelectric polarization. The heterostructures grown on these orientations are receiving a lot of focus due to their potential improvement on the efficiency of optoelectronic devices. In the present chapter, the growth of polar and nonpolar III-nitride heterostructures using molecular beam epitaxy (MBE) system and their characterizations are discussed. The transport properties of the III-nitride heterostructure-based Schottky junctions are also included. In addition, their applications toward UV and IR detectors are discussed

Pulsed Laser Deposition of Transition Metal Dichalcogenides-Based Heterostructures for Efficient Photodetection

From the past few decades, photodetectors (PDs) are being regarded as crucial components of many photonic devices which are being used in various important applications. However, the PDs based on the traditional bulk semiconductors still face a lot of challenges as far as the device performance is concerned. To overcome these limitations, a novel class of two-dimensional materials known as transition metal dichalcogenides (TMDCs) has shown great promise. The TMDCs-based PDs have been reported to exhibit competitive figures of merit to the state-of-the-art PDs, however, their production is still limited to laboratory scale due to limitations in the conventional fabrication methods. Compared to these traditional synthesis approaches, the technique of pulsed laser deposition (PLD) offers several merits. PLD is a physical vapor deposition approach, which is performed in an ultrahigh-vacuum environment. Therefore, the products are expected to be clean and free from contaminants. Most importantly, PLD enables actualization of large-area thin films, which can have a significant potential in the modern semiconductor industry. In the current chapter, the growth of TMDCs by PLD for applications in photodetection has been discussed, with a detailed analysis on the recent advancements in this area. The chapter will be concluded by providing an outlook and perspective on the strategies to overcome the shortcomings associated with the current devices

Group III-Nitrides and Their Hybrid Structures for Next-Generation Photodetectors

In the last few decades, there has been a phenomenal rise and evolution in the field of III–Nitride semiconductors for optoelectronic applications such as lasers, sensors and detectors. However, certain hurdles still remain in the path of designing high-performance photodetectors (PDs) based on III-Nitride semiconductors considering their device performance. Recently, a lot of progress has been achieved in devices based on the high quality epilayers grown by molecular beam epitaxy (MBE). Being an ultra-high vacuum environment based-technique, MBE has enabled the realization of high-quality and highly efficient PDs which have exhibited competitive figures of merit to that of the commercial PDs. Moreover, by combining the novel properties of 2D materials with MBE-grown III-Nitrides, devices with enhanced functionalities have been realized which would pave a way towards the next-generation photonics. In the current chapter, the basic concepts about photodetection have been presented in detail, followed by a discussion on the basic properties of the III-Nitride semiconductors, and the recent advancements in the field of MBE-grown III-Nitrides-based PDs, with an emphasis on their hybrid structures. Finally, an outlook has been provided highlighting the present shortcomings as well as the unresolved issues associated with the present-day devices in this emerging field of research

Harvesting energy via stimuli-free water/moisture dissociation by mesoporous SnO2-based hydroelectric cell and CuO as a pump for atmospheric moisture

Water dissociation, in general, requires external stimuli such as light energy or electricity. Here, we present a stimuli-free water dissociation using mesoporous SnO2-based hydroelectric cell that can directly be exploited to generate electric power for portable applications. The device configuration is almost identical to metal-air batteries but follows altogether a different reaction pathway. The mesoporous SnO2-based hydroelectric cell dissociates water molecule into hydroxyl ions (OH-) and hydronium ion without any stimuli, transports hydronium ions to the opposite end, and simultaneously acts as the separator. The OH- react with Al electrode to release the electrons, whereas hydronium ions get reduced at the Ag electrode to produce a potential difference as high as similar to 1000 +/- 20 mV between the electrodes that is stable over 3500 hours. The device also shows its potential toward electric power generation from atmospheric moisture with the help of CuO layer that acts as moisture pump

Topological phenomena at the oxide interfaces

Topological phenomena at the oxide interfaces attract the scientific community for the fertile ground of exotic physical properties and highly favorable applications in the area of high-density low-energy nonvolatile memory and spintronic devices. Synthesis of atomically controlled ultrathin high-quality films with superior interfaces and their characterization by high resolution experimental set up along with high output theoretical calculations matching with the experimental results make this field possible to explain some of the promising quantum phenomena and exotic phases. In this review, we highlight some of the interesting interface aspects in ferroic thin films and heterostructures including the topological Hall effect in magnetic skyrmions, strain dependent interlayer magnetic interactions, interlayer coupling mediated electron conduction, switching of noncollinear spin texture etc. Finally, a brief overview followed by the relevant aspects and future direction for understanding, improving, and optimizing the topological phenomena for next generation applications are discussed