Structure And Transport Properties In Terahertz Quantum Cascade Laser

Terahertz(THz) quantum cascade lasers(QCL)is an important kind of semiconductor radiation sources, because of its small volume, light, easy integration, frequency with the characteristics of high energy conversion efficiency. This thesis mainly studied the transport properties of THz QCL and designed THz QCL with optical phonon scattering.Firstly,the transmission coefficient of double base and single trap structure Al _{0 .3} Ga_0.7As/ GaAs / Al _{0 .3}Ga_0.7As is deduced using the transfer matrix method, and the quasi-bound state energy level in different conditions is calculated. And then calculated the relationship between electric intensity and energy level with the width of the second barrier changing. We come to the conclusion that the width of the barrier , the width of the barrier and bias of system has an significant influence to transmission coefficient. The ground-state and the first excited state image coincided when the second width of the barrier is different. fixing the first base width and changing the second base width,the system of the ground-state energy levels and the first excited state were not affected by base width .Then,in the third barrier and double well structure , this paper studies the influence to the coupled function of wells due to the middle well width . With the well width decreased ,the coupling between adjacent trap strengthened gradually.Finally,studied the transport properties of THz QCL and designed a THz QCL with optical phonon scattering. Simulated the wave function distribution and the energy level position. For design of structure, simulated high energy level wave function and low energy level wave functions of the launched region can overlap; Emission wavelength is 147.6(μm) and frequency is 2.03(THz) belong to terahertz frequencies ; Extracting area emit electromagnetic waves energy is 26.9(meV) , and equal to the lattice optical phonon energy. This is helpful to particle count reversal and increase the intensity of terahertz launch.