【作者】 刘静；

【导师】 郑卫民；

【作者基本信息】 山东大学 ， 理论物理， 2010， 硕士

【摘要】 量子限制杂质远红外发光器是种全新的器件,它可以发射波长在太赫兹区域,是目前远红外发光材料和器件研究的一个热点。本文围绕远红外发光器这一主题,以对太赫兹发光器的理论研究为切入点,开展了对太赫兹发光器材料的选择、器件制备以及特性分析的研究。本文首先介绍了基于量子点的远红外发光器件的研究背景,延伸出太赫兹频率的广泛应用及其辐射和探测技术,然后回顾半导体量子点的研究进展及存在的问题,从而引入本论文的工作---太赫兹远红外发光器件,给出了远红外发光器件制备的基本原理和采用的外延生长方法。基本原理是在量子限制效应下的杂质原子可以作为单电子量子点,可以发射太赫兹频率,用于制作远红外发光器件。我们是采用通过生长半导体超品格常用的分子束外延方法(MBE)制备了半导体低维GaAs/AlAs量子阱系统,并在GaAs量子阱中delta-掺杂受主Be原子制成我们所需要的样品结构,然后利用此样品通过半导体工艺制备出δ-掺杂GaAs/AlAs多量子阱远红外发光器件。测量了器件的一些电学参数和光学参数,加以解释,从而对提高器件的发光效率提供依据,并进行了相关的理论计算。利用分子束外延方法在半绝缘(100)GaAs衬底生长GaAs/AlAs三量子阱,阱宽10nm,垒宽5nm,在生长过程中对中间量子阱delta注入受主Be原子,掺杂浓度为5×1010 cm-2,其他两阱未作掺杂,制成样品结构。利用此样品通过分割、脱脂、刻蚀、电极接触金属化等工艺过程制作出δ-掺杂GaAs/AlAs多量子阱电注入远红外Teraherz原型发光器件。这种器件为利用量子限制杂质原子态之间的跃迁来研发固态太赫兹激光器系统提供了一定的可能性,优点是：通过MBE技术可以精确控制生长；能级结构具有可调性以及量子点所具有的一般物理性质。实验上测量得到4.5K下器件的电致发光谱(EL)和电传输特性(I-V曲线),这为进一步改善器件的发光性能、提高发光效率提供了理论依据。在外加偏压V=2.OV下EL发射谱中清楚地观察到在222cm-1处宽的尖峰,这是来源于铍受主奇宇称激发态到它的基态的辐射跃迁,而非辐射弛豫过程则使发射谱的信号很弱,这是我们今后需要改进的方面。另外在4.5K下的I-V曲线中0.72伏和1.86伏的位置出现两个共振隧道贯穿现象,分别对应于中间delta-掺杂量子阱受主能级1S3/2(Γ6+Γ7)到左边非掺杂GaAs量子阱中HH带及右边非掺杂GaAs量子阱中HH重空穴带到中间掺杂GaAs量子阱中铍受主杂质原子奇宇称激发态2p5/2(Γ6+Γ7)能级的共振隧穿。理论上研究了量子限制效应对限制在GaAs/AlAs多量子阱中受主对重空穴束缚能的影响,应用量子力学中的变分原理,数值计算了受主对重空穴束缚能随量子阱宽度的变化关系,以及变分参数随量子阱宽度的变化曲线,所取的量子阱宽度从3nm到30nm的范围,与实验值相比较发现理论计算和实验结果符合的较好。更多还原

【Abstract】 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.更多还原