Examination Committee

Prof Wei Min DAI, CHEM/HKUST (Chairperson)
Prof Kei May LAU, ECE/HKUST (Thesis Supervisor)
Prof Charles SURYA, Department of Electronic and Information Engineering, The Hong Kong Polytechnic University (External Examiner)
Prof Man Sun CHAN, ECE/HKUST
Prof Patrick YUE, ECE/HKUST
Prof Iam Keong SOU, PHYS/HKUST

Abstract

Recent decades have witnessed a booming development of III-nitride optoelectronic devices where a direct tunable bandgap is essential for efficient light emission in the green to ultra-violet regime. Other material characteristics such as high breakdown field strength, large saturated velocity, and excellent electron transport properties of III-nitrides can be exploited for high frequency and high power device applications. Sharing the same material system, monolithic integration of III-nitride devices can enable high-level integrated systems with novel functionalities and improved reliability while trimming size, cost and undesirable parasitics.

In this thesis, monolithic integration of III-nitride devices has been investigated by selective epitaxial growth (SEG). Initial demonstration was obtained by SEG of AlGaN/GaN high electron mobility transistors (HEMTs) on InGaN/GaN light emitting diodes (LEDs) to realize a voltage-controlled light emitter. Later versions feature a metal-interconnection-free laterally integrated HEMT-LED devices. To maximize device performance for both the LED and HEMT, a GaN/AlN buffer platform was developed, with high buffer resistivity and excellent crystalline quality simultaneously. With the GaN/AlN buffer, a high-brightness and low-leakage laterally integrated HEMT-LED was achieved. An Enhancement-mode GaN VMOS-LED integration was also demonstrated for the first time.

With the well-developed buffer platform and selective etching/growth techniques, a monolithically integrated micro-opto-electronic system (MOES) was built. The voltage-controlled light emitter was further integrated with a blue InGaN/GaN multi-quantum-well photodiode and an ultraviolet AlGaN/GaN Schottky barrier photodiode. This is the first demonstration of a monolithically integrated voltage-controlled light emitter with dual-wavelength photodiodes on a chip. Afterwards, the well-developed HEMT-LED-PD integration was transferred onto Si substrates, which makes further integration of III-nitride devices with conventional Si ICs possible. This demonstration brings a variety of potential applications, such as smart lighting, on-chip optical interconnect and optical wireless communication.