STUDY OF III-NITRIDES HETEROSTRUCTURE GROWN BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY (PAMBE)

Presenter	:	CHIN CHE WOEI
E-mail	:	-
Date	:	8 / 5 / 2009
Time	:	3.00 PM
Venue	:	MAKMAL KOMPUTER (269), ARAS 2, PUSAT PENGAJIAN SAINS FIZIK
Sypnosis	:	III-nitrides heterostructures have attracted a great deal of attention on their potential use in optoelectronics and high temperature/high power electronic devices due to their exceptional properties, such as the direct and wide band gap as well as high thermal stability. Moreover, III-nitride has great potential for nanoelectronic applications. Hence research on the nanostructures and doping of GaN has become intensive in recent years. MBE is the most promising epitaxial growth method owing to precise control of growth parameters, which significantly improve the film properties, composition, and thickness. In this work, the focus is on the studies of the growth of III-nitride heterostructures for the purpose of developing the new MBE system in this school. The studies include the growth of AlN buffer layer on the substrates for the preparation to grow III-nitrides epitaxial layers. For exploratory works, the growths were carried out on Si (111) and sapphire (Al2O3) instead of 6H-SiC which is expensive and commonly used. To achieve good quality GaN film on Al2O3, nitridation and AlN buffer layer were applied to overcome the issue of lattice mismatch. An in situ Ga cleaning was done on Si for removing the SiO2 by formation of Ga2O3 before deposition of the AlN buffer layer. The thin film surface morphology during the growth was investigated systematically using reflection high-energy electron diffraction (RHEED) technique. In this work, the doping process during epitaxial growth of III-nitrides heterostructures was investigated. N-type GaN and p-type GaN were successfully grown on Si (111) and sapphire. III-nitride ternary alloy, InGaN was also successfully grown on Si (111) in this study. The use of quantum dots (QDs) is more effective in nitride semiconductors since the zero-dimensional electronic states in the QDs play an essential role for improving threshold current in wide bandgap semiconductors. Therefore, the growth of InGaN quantum dots was also studied in this work. The InGaN quantum dots were successfully grown on sapphire at reduced temperature and without any growth interruption. The electrical, structural and optical properties of the samples were investigated by using Hall effect measurements, scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and Raman spectroscopy. Detection of hydrogen gas is one of the potential industrial applications, for instance, the use of hydrogen sensors in monitoring and controlling hydrogen amount in hydrogen fuel cell, as well as hydrogen storage and distribution system. N-type GaN grown on sapphire was selected for the purpose of fabricating hydrogen gas sensor. The hydrogen detection sensitivity of the device under 0.5% hydrogen concentration was measured. The results show that the GaN materials system appears to be very promising for use in hydrogen gas detection.

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