THESIS
2018
xvi, 121 pages : illustrations ; 30 cm
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. Benefiting from the mature
technology of GaN devices (LED, HEMT, etc.) and the reliable and robust properties of
III-nitride semiconductor itself, III-nitride materials show great potential to serve as an
integrated optoelectronic platform. However, until now, only few works have been done on
the monolithic integration of GaN devices. So more research works are still needed...[
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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. Benefiting from the mature
technology of GaN devices (LED, HEMT, etc.) and the reliable and robust properties of
III-nitride semiconductor itself, III-nitride materials show great potential to serve as an
integrated optoelectronic platform. However, until now, only few works have been done on
the monolithic integration of GaN devices. So more research works are still needed to further
increase the integration level and add more functions to the GaN-based integrated
optoelectronic circuit.
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 as the p-GaN contact and
achieve a great improvement (22%~27%) 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 and light intensity dimming functions. 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 and demonstrates the potential for high speed and harsh
environment light detection.
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