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This work will describe the influence of molarity and time of potassium hydroxide etching on Al-rich AlGaN layer. With potassium hydroxide (KOH) molarity of 5 mol/L, no significant change on the pores formation was observed for 5 and 10 minutes of etching. Nonetheless, there was a possibilty that some of the Ga atoms were eliminated for 10 minutes of etching, resulting in co-existance of AlGaN material with higher Al content. Similar behaviour was also witnessed in the case for 10 mol/L of KOH with 5 and 10 minutes of etching. Nonetheless, well-defined hexagonal patterns were only formed when the etching was conducted using 10 mol/L of KOH for 10 minutes. Such patterns have the potential to increase light extraction efficiency of UV LEDs.

The indium composition in InxGa1-xN/GaN multi-quantum well structure e(MQW) is crucial because lower indium composition will shift the wavelength towards ultraviolet region. Nevertheless, at certain indium content in MQW, it will out diffuse from the MQW resulting in the wavelength shift from green to much shorter wavelength, after the annealing process for p-type activation. In this study, we had grown a full Light Emitting Diode device with the MQW layer at a relative high temperature for green LED with indium pre-flow at the top of n-type layer just beneath the MQW using Metal Organic Chemical Vapor Deposition (MOCVD). Transmission Electron Microscopy (TEM) image of the MQW prior and post the activation of p-type had been observed, which resulted in good contrast, showing the abruptness of the MQW layer of the device. Homogenous layers of InxGa1- xN/GaN has been observed. We also managed to reduce the wavelength shift of the device significantly. The optical, crystal properties of grown devices had been studied.

In this work, AlN single layer has been successfully grown on c-plane sapphire using metalorganic chemical vapor deposition (MOCVD) at low reactor pressure. The effects of growth temperature, ammonia (NH3) flux and trimethylaluminum (TMAl) flux towards AlN growth were investigated. It was noted that the reaction between NH3 and TMAl has affected the growth rate across the growth temperature. Field emission scanning electron microscopy (FESEM) equipped with Energy-dispersive X-ray (EDX) have revealed the formation of AlN single layer on the sapphire substrate and elemental composition of the layer, respectively. The dependence of growth rate on growth temperature, TMAl flux and NH3 flux was observed. It could be related to the occurrence of parasitic reaction as a result of theunintentional formation of AlON composition in the AlN layer. A relationship was drawn, whereby an increase in TMAl flux and decrease in NH3 flux would lead to an increase in the AlN growth. In addition, a drastic increase in the AlN growth was observed at high growth temperature, which was more than 1000°C. Further characterization was carried out using atomic force microscopy (AFM) and phase analysis using X-ray diffraction system (XRD).