||In this dissertation, we studied the growth and characterization of GaN-based thin film grown by plasma-assisted molecular beam epitaxy for spintronics and optoelectronics application. |
In the spintronics applications, the AlxGa1-xN/GaN HEMT samples with varied Al composition were grown by plasma-assisted molecular beam epitaxy on GaN template. The surface morphology, structural properties and electronic properties were characterized. We obtained the highest mobility and lowest carrier concentration to be 20448 cm-2/Vs and in Al0.14Ga0.86N/GaN sample at 4K. Besides, Al0.210Ga0.790N/GaN sample with higher Al content also has great mobility as high as Al0.14Ga0.86N/GaN sample. The scattering mechanism of 2DEG transport was evaluated by temperature-dependent mobility curves. The Al0.18Ga0.82N/GaN HEMT was used to fabricate the nano-wires. The spin-splitting was obtained to be (2.4±0.3) meV and (1.2±0.3) meV for 200 nm nano-wire and100 nm nano-wire, respectively. According the result, we proposed a quantum-ring interferometer by introducing the concept of 1-D ballistic transport nano-wire, spin-Hall effect and A-B effect.
In the optoelectronic applications, we have characterized the optical properties of GaN microstructures in the shapes of microdisk, nail, and mushroom. We demonstrated that the superior luminance efficiency was observed on the oblique surfaces of mushroom-shaped GaN. Beside, the band transition mechanism of thin disk, nail-shaped and mushroom-shaped GaN was performed by low-temperature micro-PL. Moreover, we have grown the GaN layers by MBE on Si (100) substrates with sputtered AlN buffer layer. We showed with TEM images that variant kinds of GaN epitaxial planes can be grown with sputtered AlN on Si (100) substrate. It was found that zinc-blende GaN can be obtained via phase transition under certain growth condition. For LED application, the high quality InGaN/GaN MQWs has been grown by PA-MBE on GaN template.