Carrier transport in nano structured junction for sensing and lighting application

Abstract

Low dimensional nanostructured materials have attracted interest in recent years for various scientific communities because of the promising chemical, mechanical, electrical and optical properties. There exists a large variety of semiconductor with electronic devices. I will provide an overview of nanostructures junction application to light-emitting devices and chemical sensors. Chapter 1 presents the fabrication procedure of passivated Pyramid LED arrays and their improved electrical and optical properties. Three-dimensional hexagonal pyramid with InGaN/GaN multiple quantum wells (MQWs) is composed of (101(1 ) ̅) semi-polar facets. Compared with the commonly used (0001) c-plane MQWs, the semi-polar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. However, Defects present in the apex region of the MQWs and electric-field focused on the vertex due to corner effects. Therefore, it is essential to investigate defect reduction methods. Here, we report the effect of vertex passivation of Pyramid LEDs for the enhancement in the light extraction, reducing reverse leakage current and short-wavelength emission. The leakage current gets lower with the addition of the MgO passivation layer while it is successfully reduced by inserting the vertex passivation layer. With the heavily reduced leakage current, the LED with the vertex passivation layer shows quite promising performance. Chapter 2 covers of nanostructure modified sensitive and selective self-powered gas sensors based on NiO/ZnO p-n junction operated by tribo-electric generators. The performance of the room temperature VOC vapors sensing can be contributed to the coupling of the surface charge transfer of the metal oxide nanowires and reference to the levels of wettability of solid polymer surfaces since charged surface being charged is strongly dependent on the surface adsorbed molecules. These provide the ability of a chemical gas sensor without any external power sources for operating the device, because the sensor was tested for detect various species of VOCs using triboelectric power generation. This self-powered gas sensor could be advantageous of simple fabrication, low-cost and easy application.