Study On Optical Properties Of Low-dimensional Structures In Semiconductor

THz of the electromagnetic spectrum is in a unique position and has many advantages and potential value in use, so in the far-infrared band the theoretical and experimental studies of Terahertz light-emitting devices or lasers naturally become a hot spot in the world today.The direction of the physical phenomena which has been demonstrated by the semiconductor quantum dots in has a good prospect.Therefore, compared to other THz devices, people pay more attention to the research of quantum dots devices, Although the preparation of quantum dots has been researched and the better preparative techniques of quantum dots have also benn invented in many years, in order to prepare good and precise controlled quantum dots, quite a lot of efforts still have to be paid.To overcome deficiencies in the technical preparation of quantum dots, a single-atom impuritiy in semiconductor quantum well has been proposed. By adjusting the quantum confinement effect of impurity atoms in the quantum wells, the structure of impurity atomic energy levels can be manipulated, in particular, the interval of energy levels between the impurity levels can be controlled and the ranking of energy levels can be adjusted, which form single-electron quantum dots or single-hole quantum dots.Experimentally, advanced molecular beam epitaxy growth technique was used, respectively, A series of alternating the growth GaAs/AlAs multiple quantum wells with well widths ranging from 30 to 200 (?) along the direction of (100)GaAs substrate and a single epilayer of GaAs uniformly Be doped were prepared. Be acceptor atoms in 8-doped were doped at the center of all the multiple quantum well samples with different well widths. The studies of all the samples were mainly made in the low temperature 4.2K, respectively, the observations and analysis of PL spectra, resonance Raman scattering spectroscopy and Fourier transform infrared absorption spectra were done.In the PL spectra, in addition to the free excitons, acceptor bound exciton and free to bound the transition, more importantly, the two holes transitions (THT) which are related to the acceptor bound exciton were observed,. Based on an analysis, the energy interval between the two peaks of Be0X and THT would correspond to the energy which was needed from the ground state 1S3/2 (Γ6+Γ7) to excited state 2S3/2 (Γ6+Γ7). In addition, other transitions from the ground state to the even-parity excited states can be seen in multi-quantum wells experiments,. Thus we come to the conclution of the energy level transitions from acceptor ground state to the even-parity excited states with different quantum well widths.In resonance Raman scattering spectrum, h01 (caused by hole sub-band transitions which are inspired by light), and the LO and TO phonons which are related to GaAs layer were clearly observed.In addition, the high-energy side of the resonance Raman scattering spectra is the peak with very wide half-width which is the interface phonons (IF), the peak which is the acceptor atom-related local vibration mode and the peak of interface states. Beyond that, the expected accepter-related even-parity transition peaks were not observed in this experiment, the reasons could be the small experimental scattering cross section, low pump power and so on.In Fourier transform infrared absorption spectra,different quantum well width samples were observed, it was clear that three major intraband transition absorption lines which were respectively derived from trantions of the acceptor ground state to the three odd-parity excited states were seen.From the above experimental studies, it can be obtained the relationship between the quantum well width and the accepter transition energy.from this relationship, it is found that the transition energy of acceptors increases as quantum well width decreases. In addition, it can be seen that the 2P level of accepters is under the 2S level. According to quantum mechanics transition selection rules, when the quantum well lasers are manufactured, if you can meet the carriers population inversion, carriers will give priority to enter the 2P level, to improve the efficiency of the corresponding light-emitting device.