Optimizing performance and yield of vertical GaN diodes using wafer scale optical techniques

To improve the manufacturing of vertical GaN devices for power electronics applications, the effects of defects in GaN substrates need to be better understood. Many non-destructive techniques including photoluminescence, Raman spectroscopy and optical profilometry, can be used to detect defects in the substrate and epitaxial layers. Raman spectroscopy was used to identify points of high crystal stress and non-uniform conductivity in a substrate, while optical profilometry was used to identify bumps and pits in a substrate which could cause catastrophic device failures. The effect of the defects was studied using vertical P-i-N diodes with a single zone junction termination extention (JTE) edge termination and isolation, which were formed via nitrogen implantation. Diodes were fabricated on and off of sample abnormalities to study their effects. From electrical measurements, it was discovered that the devices could consistently block voltages over 1000 V (near the theoretical value of the epitaxial layer design), and the forward bias behavior could consistently produce on-resistance below 2 mΩ cm2, which is an excellent value considering DC biasing was used and no substrate thinning was performed. It was found that high crystal stress increased the probability of device failure from 6 to 20%, while an inhomogeneous carrier concentration had little effect on reverse bias behavior, and slightly (~ 3%) increased the on-resistance (Ron). Optical profilometry was able to detect regions of high surface roughness, bumps, and pits; in which, the majority of the defects detected were benign. However a large bump in the termination region of the JTE or a deep pit can induce a low voltage catastrophic failure, and increased crystal stress detected by the Raman correlated to the optical profilometry with associated surface topography.

Industrial Smart Energy Metering Controlling and Automation with the Help of Android

In this research a special type of meter is developed which can measure various important parameters of electrical energy and as well as give users the access to cntrol the appliances which are connected to it through the designed android application. Initially measurement of the current is performed with the help of Hall Effect sensor, as this method is very accurate. In second part supply voltage is calculated with the help of transformer and DC biasing method. This method is also very accuratefor measurement of voltage. By multiplying the above measured current and voltage, apparent power is obtained. Finally, the energy parameter is obtained. In this research, a special type of meter is designed which can measure electrical current, voltage, power and energy with accuracy around 99%. These obtained parameter results will be directly uploaded to Google firebase which is connected to our android app. Any user having this application installed will take this reading live to their smart phones as well as their web browser

Novel DC-biasing circuits with arbitrary harmonics-control capability for compact high-efficiency power amplifiers

The next generation mobile communication systems impose challenging performance, size, and cost requirements on the power amplifiers (PAs). This paper presents novel DC-biasing circuits, which are compact and yet can control the harmonics almost arbitrarily. The proposed circuit consists of a composite right-/left-handed (CRLH) transmission line (TL) stub, of which the size and harmonics-control function can be tuned by modifying the dispersion diagram of the stub line. As a proof of concept, a compact 2-GHz 7-W GaN HEMT class-F PA using the versatile CRLH-TL stubs was fabricated, demonstrating 85.8% drain efficiency and 77.3% power-added efficiency.