External Field Effect On The Electronic State In Galnasp/inp Stepped Quantum Well

Quantum well semiconductor lasers, with good small-signal modulation frequency response,can be used as the best light source in the information superhighway. They take advantage of away of direct modulation to complete the transmission of the signal. Because of its advantages oflow threshold current, narrow spectral line width, high characteristic temperature, high quantumefficiency and output power, quantum well semiconductor lasers greatly improve transmissionspeed and performance of optical communications. Quantum well semiconductor lasers also hasgood application prospects in optical communications, optical interconnects and opticalinformation processing. Thus, more and more extensive experimental and theoretical works havebeen devoted to the research on low-dimensional semiconductor devices used in the field ofoptical communications in recent years. In this thesis, we study the electron states inlow-dimension semiconductor quantum well structures in the framework of effective-massenvelope function theory using the variational method. The main contents are presented asfollowing:1. The development trend of low-dimensional semiconductor optoelectronic devices and theimpact of low-dimensional semiconductor optoelectronic devices for optical communication areintroduced systematically, and some typical applications of several low-dimensionalsemiconductor optoelectronic devices are described in optical communication. The electronicstructure and properties of low-dimensional semiconductor materials and electronic states of themain theoretical calculation method are also discussed in detail, as well as control of doping anddefects in the material.2. Within the framework of effective mass approximation, the electronic state of a hydrogenicdonor impurity in GaxIn1-xAsyP1-y/InP single quantum well is detailedly calculated using thevariational method. The ground state energy and binding energy are calculated with or withoutimpurities, and the quantum well width, alloy concentration and donor impurities are discussedabout the influence on the binding energy of hydrogenic donor impurity. The results show that areasonable barrier width should be chosen for the better calculating and the binding energy of thefirst excited state is much larger than the ground state. The ground state energy and the donorimpurity binding energy decreases with the well width increases, and stabilized gradually. Thebinding energy of impurity peaks at a relatively small width value and reaches its maximumwhen the donor impurity is located at the center of the quantum well.3. The influence of applied electric fields and stepped quantum wells height onGaxIn1-xAsyP1-y/InP hydrogenic donor impurity electronic state are investigated. The results showthat the hydrogen impurity binding energy reaches its maximum when the donor impurity islocated at the center of the stepped quantum wells. The applied electric fields drive the electron wave function away from the stepped quantum well center, and induce asymmetric distributionof the donor binding energy. The variation of Ga and As content leads to the correspondingchanges in the stepped quantum well height, which significantly affects the binding energy ofhydrogenic impurities in the stepped quantum wells. The results are meaningful and can beapplied in the design of optoelectronic devices based on stepped quantum wells.4. We have investigated the effects of the magnetic field on the binding energy of the hydrogenicimpurities in GaxIn1-xAsyP1-y/InP stepped quantum well. The binding energy of hydrogenicimpurity, with different stepped well widths, as a function of the impurity positions and as afunction of the magnetic field are given. When the donor impurities are located in the steppedquantum well center, the impurity binding energy reaches its maximum with the smaller steppedwell width and lager magnetic field. With the influence of magnetic field of the bending tilt andthe lager well width, the binding energy of a hydrogenic impurity increases significantly, evenobtains its maximum value at the impurity position away from the well center. The more Ga、Asconcentrations and magnetic field are added, the lager impurity binding energy will be. Thecalculation results has a certain reference value on the new magneto-optical modulator based onthe stepped quantum well structure.