Thesis Examination Committee

Prof Xiangru ZHANG, CIVl/HKUST (Chairperson)
Prof Kei May LAU, ECE/HKUST (Thesis Supervisor)
Prof Anthony H W CHOI, Department of Electrical and Electronic Engineering, The University of Hong Kong (External Examiner)
Prof Man WONG, ECE/HKUST
Prof Philip Kwok Tai MOK, ECE/HKUST
Prof Ricky Shi-Wei LEE, MAE/HKUST

 
Abstract

Optoelectronic Integrated circuits (OEICs) have found many applications in short-distance communication, intelligent displays and sensing. With the increasing demand for higher speed, more functions and higher integration level, the silicon based OEIC shows weaknesses due to the limit set by the silicon material properties. Thus, researchers are trying to find alternative solutions in compound semiconductors. However, until now, only few works have been done on the monolithic integration of GaN devices. 
 
In this thesis, we are focusing on developing the monolithically integrated GaN devices for lighting and detection applications. To achieve this, we first integrate discrete LEDs in series into a flip-chip high voltage LED (HVLED) to serve as an effective light source. During the fabrication process, we develop a curable-polymer trench-filling technique. Our HVLED shows small forward voltage variation, uniform light emission, linear light output, and stable thermal performance. When using the HVLED in a low-flicker lighting system, the lighting system shows a flicker percentage as low as 17%. At the same time, we also try a pre-annealed Ni/Ag scheme to replace the conventional ITO scheme and achieve a great improvement in efficiency. Then we integrate an LED with a GaN HEMT to achieve a fast modulated voltage-controlled light emitter, namely the HEMT-LED device, for light signal transmitting with a high date rate of 16.7 Mbit/s and a light intensity dimming range of 0.1%-100%. Furthermore, we integrate a GaN HEMT with a metal-semiconductor-metal photodiode (MSM-PD) and other on-wafer passive components (feedback resistor and capacitor) based on the same GaN HEMT epitaxial structure. The monolithically integrated photoreceiver can respond well with a modulated UV light signal at 100 kHz and demonstrates the potential for harsh environment light detection.