| At present,microelectronic and optoelectronic devices are developing rapidly,and the performance of devices such as HEMT,photodetectors and lasers is improving rapidly.With the advantages of high electron mobility and photoelectric conversion efficiency,Ⅲ-Ⅴ semiconductor materials have been important materials for microelectronic and optoelectronic devices.The quality,composition and doping concentration of AlGaAs films directly affect the optoelectronic performance of the devices.MBE is a key epitaxial device for the preparation of related devices,It has the advantages of precisely controllable growth rate and temperature,and the grown materials are smooth and less flawed.In this paper,we focus on the epitaxial growth of AlGaAs/GaAs and the preparation process of related materials and devices,and carry out theoretical analysis and experimental process exploration.The main research contents and results of this thesis are as follows.1.The theoretical basis and experimental methods of MBE epitaxial equipment and related characterization means are summarized.Mastered the working principle of MBE devices and growth mechanism.Mastered epitaxial characterization methods and analysis methods.Measure the component and other information of the samples by X-ray double crystal diffractometer;measure the doping concentration of the samples by electrochemical C-V;test the electrical properties of the samples by Hall effect;observe the surface morphology of the samples by scanning electron microscope.2.Various epitaxial structure growth experiments were carried out using MBE to improve the epitaxial growth process,firstly,the experiments on the control of growth conditions of AlGaAs materials by molecular beam epitaxy:the Si-doped and Be-doped GaAs films with different gradients were epitaxially grown to obtain the control process of doping concentration;the Alx Ga1-xAs films were epitaxially grown to be able to adjust the Al component size according to the beam current;secondly,designed and grown several groups of HEMT materials to verify the maturity of the growth process,and Hall effect tests were performed,and the mobility reached 7966 cm2/V·s at room temperature and 141,208 cm2/V·s at 77 K,which reached the expected experimental results.3.The key processes for microstructure preparation in the device preparation process were explored.The principle of changing the etch rate and pattern steepness of GaAs-based materials by equipment parameters and process gas ratio was explored.It was learned experimentally that increasing the SiCl4 flow ratio,chamber pressure,RF bias power and ICP source power would increase the etch rate,but each would not have the same mechanism of influence,and also have an effect on the material steepness,while increasing the ratio of Ar and N2 would decrease the etch rate,with N2 having a greater effect on the etch steepness,which would reach 90° with decreasing N2.The etching parameters with suitable etching rate,good etching steepness and 0.97%surface uniformity are obtained,which lay the foundation for further improvement of semiconductor device preparation process.4.The GaAs-based PIN photodetector was designed and grown,and the photodetector was successfully fabricated to verify the perfection of the epitaxial process and the device fabrication process.The high speed performance was tested and analyzed,and a 38μm diameter detector with a 3dB bandwidth of 14.8GHz at an applied reverse bias of 3 V and 850nm incident light was obtained,and the problems encountered during the epitaxy process and the fabrication process were analyzed and optimized. |
