The Growth of Ga-related Semiconductors and their Application for photodetectors

Abstract

The main goals of this dissertation are the growth of GaN Ga2O3 and InGaN and the fabrication and analysis of photodetectors (PDs) First we reported the growth of β-Ga2O3 cap layer by furnace oxidation of GaN epitaxial layer at high temperature in oxygen containing ambient to the fabrication of the GaN-based PDs With the β–Ga2O3 cap layer inserted it was found that we could reduced reverse leakage current by more 4 orders of magnitude and increased the UV-to-visible rejection ratio by 21 times With a 5-V applied bias the normalized detectivity were 1 01x1013 and 1 28x109 cmHz0 5W-1 for the PDs with and without the β–Ga2O3 cap respectively On the part of InGaN/GaN multi-quantum-well (MQW) PDs with a β–Ga2O3 cap layer the reverse leakage current by at least about 2 orders of magnitude with a 5-V applied bias because it created a thicker and higher potential barrier with a beta-Ga2O3 cap layer The reverse leakage current can be further reduced and a 90-fold larger ultraviolet-to-visible rejection ratio can be achieved by using InGaN/GaN MQW layers which confine the electron-hole pairs generated by lower-energy photons In addition the noise level was reduced and detectivity was increased With a 5-V applied bias the noise equivalent power and normalized detectivity were 8 4×10-13 W and 7 9×1012 cmHz0 5W-1 respectively Based on the aforementioned the InGaN/GaN multi-quantum-well (MQW) PDs were covered with Au nanoparticles to increase performance The reverse leakage current decreased by more than 3 orders of magnitude with a 5-V applied bias a 225-fold increase of the rejection ratio (250/3385 nm) was achieved with a 1-V applied bias and a 3 9-fold enhancement in rejection ratio (375/430 nm) with a 1-V applied bias could be achieved after the PDs were covered with Au nanoparticles There was an obvious response at 500 nm due to the surface plasmon resonance in Au nanoparticles The results indicate that Au nanoparticles can be used to improve the performance of optoelectronic devices

Date of Award	2014 Jan 14
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)