Far-infrared Emitter Design Based On Quantum Confined Impurity And The Related Calculation

Light emitting devices designed based on quantum confined impurity have proven their cability and versatility with the realization of high performance operating for far-infrared wavelength. The study on the GaAs/AlGaAs quantum well infrared emitter is a hotspot in the field of the research on infrared materials and infrared apparatus. In this thesis, picking the THz illuminator as the point of penetration, this article carried out research on material select,device fabrication and character analysis of the THz illuminator.First, this article presents the research background of far-infrared emitter,which is based on quantum dots.Then it introduces the widespread use of the THz frequecy and corresponding radiation and detective technology firstly, followed by a general review of the development and problems of semicondutor quantum dots, which gives an introduce to the main work--THz infared illuminescent devices with basic fabrication principles. The basic priciple works in the way that quantum confined doped atoms by acting as single quantum dot radiate THz laser light,which is adaptable for infared illuminescence device fabrication. The GaAs/AlAs triple-quantum-well samples were grown by molecular beam epitaxy, and the middle GaAs quantum-well layer was delta-doped at the well centre with Be shallow acceptors. Then the far-infrared Terahertz prototype emitter was fabricated using the samples as mentioned. Electronic parameters and optic parameters of emitter are measured and explained, which provide basis on how to improve luminescence efficiency.The GaAs/AlAs triple-quantum-well samples were grown on GaAs (100) semi-insulating substrate,the width of quantum well and barrier is 10nm/5nm, Be doping concentration in the middle well is 5×1010cm-2, no doping in the other two wells. The sample is cleaned by trich,acetone,methanol and D.I.water in the cleaning room.Then photolithography to define mesa,and etching using H3PO4:H2O2:H2O Then evaporating metals Cr/Au for p-type,remove GaAs oxide by HCl:H2O. Last wire bonding. Through this procedure,terahertz emitter is made up.This device provides possibilities for solid THz laser device system researching by using states transition of quantum confined impurities. The advantages of such devices lies as follows:precise controlling on growth procedure by MBE techneque; adjustable energy level and universal properties that quantum dots prossess.Electroluminescence (EL) and current-voltage characteristics (I-V) were measured at 4.5 K. In the EL spectrum, a wide peak was observed clearly at 222 cm-1, which is attributed to the Be acceptor's radioactive transitions from the excited odd-parity state to the ground state. Nevertheless, the emission signal was weakened by non-radioactive relaxation processes. In the I-V curve, the negative differential resistance characteristic at the position of 0.72 and 1.86 V was also observed clearly. This is considered as the resonant tunneling between Be acceptor energy level ls3/2(Γ6+Γ7) in the middle quantum-well and the HH1 band in the left-side non-doping quantum-well, and the resonant tunneling between the HH band in the right-side non-doping quantum-well and Be acceptor 2p5/2(Γ6+Γ7) energy level respectively.We theoretically investigate the effect of quantum confinement on acceptor binding energy in multiple quantum wells. A variational calculation is presented to obtain the acceptor binding energy as a function of well width. The quantum width ranges from 3 to 20 nm. The experimental results agree well with the theory.