Chapters authored
MEMS Humidity Sensors
This chapter reviews MEMS humidity sensors fabricated using microfabrication technologies. It discusses the operation principle, different designs, and the fabrication technologies for the different sensing mechanisms. Sensing humidity using capacitive sensors is first reviewed with a highlight on the different sensing materials and how their permittivity and physical parameters affect the sensor performance. Then the chapter discusses the piezoelectric humidity sensing method, wherein piezoelectric sensors the dynamic mode measurement is used. In these sensors, the mass changes corresponding to the humidity, resulting in resonance frequency shift and amplitude change. Finally, the chapter reviews the resistive humidity sensors where the change in the resistivity of various materials is used as an indication of humidity change in the environment.
Part of the book: Humidity Sensors
Recent Advancements in GaN LED Technology
Gallium nitride (GaN)-based solid state lighting technology has revolutionized the semiconductor industry. The GaN technology has played a crucial role in reducing world energy demand as well as reducing the carbon footprint. As per the reports, the global demand for lighting has reduced around 13% of total energy consumption in 2018. The Department of Energy (USA) has estimated that bright white LED source could reduce their energy consumption for lighting by 29% by 2025. Most of the GaN LEDs are grown in c-direction, and this direction gives high growth rate and good crystal integrity. On the other hand, the c-plane growth induces piezoelectric polarization, which reduces the overall efficiency of LEDs since the last decade researchers round the globe working on III-N material to improve the existing technology and to push the limit of III-V domain. Now, the non-polar and semi-polar grown LEDs are under investigation for improved efficiency. With the recent development, the GaN is not only limited to lighting, but latest innovations also led the development of micro-LEDs, lasers projection and point source. These developments have pushed GaN into the realm of display technology. The miniaturization of the GaN-based micro-LED and integration of GaN on silicon driving the application into fast response photonic integrated circuits (ICs). Most of the recent advancements in GaN LED field would be discussed in detail.
Part of the book: Light-Emitting Diodes