Study On The Intersurfical Diffusion Of GaAs/Al_xGa_1-xAs Superlattice

GaAs/Al0.37Ga0.63As superlattice has been grown on semi-insulted GaAs(001) substrate with optimized growth conditions by molecular beam epitaxy(MBE), and then treated by rapid thermal annealing at high temperature. Photoluminescence(PL) and double crystal X-ray diffraction(DXRD) measurements were performed in order to demonstrate the intersurficial diffusion in superlattice, and the intersurficial diffusion length is also calculated using these results. Furthermore, the modification of infrared detectivity by the intersurficial diffusion is also investigated. This paper includes the following four parts:Chapter one introduces the development of infrared photodetectors at home and abroad, the growth techniques of superlattice materials and the basic theory of intersurficial diffusion in superlattice.Chapter two introduces the principle of MBE, manufacture of superlattice, the treatment to the superlattice by raipd thermal annealing at high temperature and measure methods of samples.Chapter three is results and analysis of experiment. superlattice materials of GaAs/Al0.37Ga0.63As have been successfully grown on semi-insulted GaAs(001) substrate by molecular beam epitaxy, and then treated by rapid thermal annealing at 650℃,800℃,850℃for 60s, respectively. PL spectra and DXRD rocking curve of samples are measured. The PL spectra show that the energy peak resulting from the recombination of electrons on the first excited state in GaAs quantum well and holes on acceptor level in AlGaAs barrier shift to high energy after rapid thermal annealing at 800℃and 850℃.The DXRD rocking curve show that the peak intensities decreases dramatically after annealing at 800℃and 850℃. But, the sample treated at 650℃has little variety in comparing with the as-grown sample. The intersurfical diffusion length is also calculated using these results respectively, and the agreement of intersurficial diffusion length value between PL and DXRD results is reasonable.Chapter four demonstrates modification of infrared detectivity by the intersurficial diffusion. The electronic energy structure in GaAs/Al0.37Ga0.63As superlattice is calculated based on the general formalism of the Kronig-Penny model. The calculated results show that the initial infrared detective response wavelength can shift from 7.73μm to the atmosphere window between 8μm and 14μm after rapid thermal annealing.