| Summary: | 博士 === 國立交通大學 === 光電工程系所 === 94 === GaN materials are very interested for their direct wide bandgap structures and many advantages of material properties. Therefore they are likely to be the basis of a strong development of novel family semiconductor devices, for optronics as well as for electronics. Recently, III-V nitride semiconductors have been the commercial productions with a extremely wide applications; high brightness light emitting diodes (LEDs) emitting from green to near UV can be used as any kind of lighting, room-temperature violet laser light emission has paved the way to wider possibilities in optical storage, and high-power, high-temperature electronic devices have been used in harsh environments like automotive engines, space, and avionics.
In this study, in order to develop new generation device and to resolve some material issues on nitride-based light emitting devices, we have developed the optical and electric quantum confined structure grown by metal organic chemical vapor deposition (MOCVD). They are included the developments of GaN-based microcavity structures and InGaN Quantum dots (QDs) structure.
For the fabrication of high quality nitride-based microcavity structures, we started this study from design and simulation to obtain a high reflectance nitride-based distributed Bragg reflector (DBR) with a reasonable numbers of pair and stopband width in DBR structure. The monolithically grown AlN/GaN DBR structure has been demonstrated and the fabrication issues of AlN/GaN DBR structure have been resolved. By optimizing the growth condition and developing an non-quarterwave stacks DBR structure to control the accumulative strain energy, A high reflectance AlN/GaN DBR structure with crack-free surface have been successful growth.
Using the high reflectance AlN/GaN DBR as the bottom mirror, and a dielectric oxide DBR structure as the top mirror, we have fabricated a 3�� nitride-based microcavity with the hybrid DBR mirrors resonant structure. The feasibility of this nitride-based microcavity structure is examined by the performance of optical pumped, and the laser action has been achieved under the optical pumping at room temperature with a threshold pumping energy density of about 53 mJ/cm2. The nitride-based microcavity emits 448 nm with a linewidth of 0.25 nm. Following, the electrically driven device with nitride-based microcavity structure has been fabricated and the characteristics of the 3�� GaN-based microcavity light emitting device structures have been discussed. A much less red-shift with injection current and a higher output power caused by the resonance effect in this MCLED has been observed.
Finally, the electric quantum confined structure with a quantum dots (QDs) structure has also been grown and the characteristic were also been studied. We have grown a self-assembled InGaN QDs structure with the growth interruption by MOCVD. The density of InGaN QDs was about 4.5 x 10^10 cm^-2 with an average lateral size of 11.5 nm and an average height of 1.6 nm. The effects of the interruption time on the morphological and optical properties were studied. The results suggested that the interruption growth could modify the size of InGaN QDs and extend the emission wavelength to the short wavelength region, and at the same time improve optical quality of the QDs.
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