Research On Movpe Growth And Optoelectric Characteristics Of Alingan Semiconductor Films

AlxInyGa1-x-yN quaternary alloys have attracted considerable attention as ultraviolet (UV) light-emitting material. By varying aluminum and indium compositions, the band gap and lattice constant can be independently changed， which can be helpful to reduce dislocation density as well as piezoelectric field. Moreover, it provides much better insight into the growth process, in particular it allows to modulate the thermal expansion coefficient of AlxInyGa1-x-yN for matching better with GaN than its ternary counterparts, which is an important advantage in epitaxial growth. According to the present research hotspots and difficulties on AlxInyGa1-x-yN quaternary alloys, we pay more attention to the MOVPE growth of high qulity and large bandgap AlxInyGa1-x-yN quaternary alloys, through adjusting the TMAl flow rate and growth temperature. The phase separation, luminous mechanism and electron-phonon interaction of AlxInyGa1-x-yN quaternary alloys were researched in details. The details are as follows:AlxInyGa1-x-yN quaternary alloys have been grown through MOVPE on sapphire by adjusting the TMAl flow rate. Furthermore the AlxInyGa1-x-yN quaternary alloys with lattice constant match with GaN buffer have been achieved through only adjusting the TMAl flow rate. The effect of the TMAl flow rate on the optical and electrical properties of AlxInyGa1-x-yN quaternary alloys were researched. The measurement result shown the Internal quantum efficiency of AlxInyGa1-x-yN quaternary alloys was higher than InxGa1-xN and GaN.AlxInyGa1-x-yN quaternary alloys have been grown through MOVPE on sapphire by adjusting the growth temperature. The effect of the growth temperature on the optical and electrical properties of AlxInyGa1-x-yN quaternary alloys were researched. As the growth temperature reduced, the emission peak intensity of AlxInyGa1-x-yN quaternary alloys enhanced obviously, while the surface RMS of increased suddenly. We believed that this is due to the low migration and high degree of surface adhesion of Al atoms, when the temperature reduce, the Al atoms can’t reach the proper position in lattice, and then formed the island growth in surface.The phase separation of AlxInyGa1-x-yN quaternary alloys were researched in details. n. For sample1, with a lower Al content (14%), there is no obvious phase separation observed. While for sample2, as the Al content increasing to18%， phase separation was formed， which might result in the formation of In-rich clusters. The simulation result by ab initio method also shows similar results. Indium content was kept at3%in that work, when the Al content increasing from8%to15%, there is no phase separation, as the Al content increasing from15%to20%, indium-rich regions were formed in the film, which indicated the occurrence phase separation with Al content increasing. The XRD results of the two samples are consistent with the previous calculation results, which demonstrate that with a comparable In content, the Al atoms play as a “catalyst” to the phase separation process in AlxInyGa1-x-yN quaternary alloys.Luminous mechanism of AlxInyGa1-x-yN quaternary alloys were researched in details. Strong phase separation in the AlxInyGa1-x-yN quaternary alloys was observed as the Al content increased, especially In-rich phase segregation. The situation here is similar to the existence of In nanoclusters in InGaN based semiconductors. At some small regions, the In-rich phase formation leads to the localized states at potential minima, which might confine the excited carriers. The localized carriers are beneficial for radiative recombination, causing the emission intensity to increase. In AlxInyGa1-x-yN film, it was reported that above a certain critical content， the Al atoms act as the “catalyst” for the phase separation process， and the In-In affinity changes increased drastically. Based on analysis above, it can be speculated that enhanced emission intensity of sample2is induced from In-cluster in the epilayer. In this case, the excitons can be localized in potential wells formed by In-nanoclusters, which enhance the overlap of neighboring excitonic wave function and large wave function overlap results in high recombination probability. Due to the existence of a large number of In-clusters in the AlxInyGa1-x-yN alloys with high Al content, therefore it can overcome the influence of a large number of defects and provide the brighter emission than that of AlxInyGa1-x-yN alloy with lower Al content.Electron-phonon interaction of AlxInyGa1-x-yN quaternary alloys were researched in details. The Huang-Rhys factor of In0.03Ga0.97N and Al0.15In0.03Ga0.82N were caculated. It can be draw that the alloy disorder has an essiontial role on the exciton-phonon interaction in AlxInyGa1-x-yN quaternary alloy. With the increasing of Al content the alloy disorder was enhanced, result in the increase both carrier localization and phonon confine which increase the ratio of exciton-phonon interaction. These sitiation reflected in the PL spectra was both the emission intensity increase of ZPL and PSB.AlInGaN film was prepared by by metalorganic vapor phase epitaxy (MOVPE). The metal semiconductor metal photodetector based on the Al0.4In0.023Ga57.7N film exhibits a. The peak responsivity of the photodetector was around290nm and a very sharp cutoff wavelenghth was at a wavelength of about310nm corresponding to the Transmission of the AlInGaN.