| Gallium arsenide（GaAs）material is a representative III-V semiconductor material.Due to its high electron mobility,good anti-irradiation ability,high photoelectric conversion efficiency and low intrinsic carrier concentration,it has been widely used in the field of semiconductor optoelectronics,mainly for the preparation of infrared semiconductor optoelectronic devices.However,GaAs nanowires have unique one-dimensional structure and small size,which can be combined with other materials to form quantum well,core-shell and other structures,and become the basic components of optoelectronic devices,which has a good application value in the future optoelectronic integration.However,GaAs-based nanowires still have many problems,such as a large number of suspension bonds on the surface resulting in high surface defect states,and long-term placement in the air will react with oxygen to produce surface oxides,thus reducing their optical and electrical properties.In order to improve the performance of optoelectronic devices,it is an urgent problem to obtain GaAs nanowires with good luminescence characteristics.Therefore,the growth methods,conditions,morphology and structure of GaAs-based nanowires and surface passivation of GaAs-based nanowires are particularly important.In this work,GaAs nanowires are passivated in two ways to improve their optical properties on the basis of the controllable growth of GaAs nanowires.One is wet passivation on the surface,the other is passivation on the Al GaAs shell.In order to broaden the emission band,GaAs/In GaAs core-shell nanowires were prepared and their optical properties were studied.The thesis mainly includes the following parts:（1）GaAs nanowires were grown on Si substrate by gas-liquid-solid（VLS）mechanism using molecular beam epitaxy.The morphology and structure of GaAs nanowires were studied by scanning electron microscopy（SEM）and transmission electron microscopy（TEM）,and their optical properties were studied by photoluminescence（PL）.The results show that GaAs nanowires have two main luminescence peaks,and their luminescence sources are bound exciton luminescence,defect luminescence and free exciton luminescence,which lays a solid material foundation for passivating surface states of GaAs nanowires in this paper.（2）（NH4）2S isopropyl alcohol solution was used to passivate GaAs nanowire,and the passivation time and the passivation solution concentration were changed respectively.It was found that the passivation of GaAs nanowire by S passivation could effectively improve the luminescence intensity of GaAs nanowire without introducing other luminescence mechanism,and obtain better surface passivation conditions.（3）GaAs/Al GaAs core-shell nanowires were grown on the basis of GaAs nanowires by molecular beam epitaxy.The structures of core-shell nanowires were measured by TEM.Meanwhile,the effects of core-shell structures on the luminescence mechanism and carrier motion of GaAs nanowires were analyzed by PL spectroscopy.On this basis,the S wet process was used to passivate GaAs/Al GaAs core-shell nanowires,and the effect of passivation on the luminescence characteristics of GaAs/Al GaAs core-shell nanowires was studied.On the surface of the study,GaAs/Al GaAs core-shell structure can effectively inhibit the high surface states in GaAs nanowires without introducing new luminescence,and S wet passivation is also applicable to core-shell nanowires.（4）In order to broaden the emission wavelength of nanowires,GaAs/In GaAs core-shell nanowires with different in components were grown by changing the equivalent in beam pressure,and characterized by X-ray diffraction（XRD）and PL spectra with variable temperature and power.The effects of in components on the band structure and luminescence characteristics of core-shell nanowires were compared and analyzed.The study shows that the core-shell structure nanowires can be regulated by regulating the composition of In.Because of the typeⅠband structure,the GaAs/In GaAs core-shell nanowires will restrict the carrier in the In GaAs trap layer,the luminescence peak is In GaAs luminescence,and introduce a new defect luminescence mechanism,and introduce more defect luminescence when the composition is too large.In this paper,high quality GaAs-based nanowires were obtained by analyzing the effects of growth parameters and S wet passivation on the growth properties of GaAs-based nanowires. |
