Transfer Matrix method for computation of electron transmission through aperiodic MQW
This paper presents the Eigen values and corresponding Eigen functions for the electron states in an aperiodic and asymmetric Multiple Quantum Well structure. A faster, simpler, and accurate algorithm based on Transfer Matrix method has been introduced for solving time independent Schrödinger equation in the most general case of aperiodic and asymmetric MQW structure. The MQWs are aperiodic with varying well and barrier widths and asymmetric i.e., having different materials and effective masses for the different regions of the wells and barriers. Adjacent wells are coupled through the barriers. Effect of barrier width on the tunneling properties has also been investigated. The theoretical results are compared with experimental results of Giorgetta et all [1]. Results of the computation based on the general model agree well with experimental data.
Resonant Tunneling in Fibonacci Series Multiple Quantum Wells Nanostructures
Tunneling of electrons through the Fibonacci series multiple quantum wells (FMQWs) has been studied theoretically within unified transfer matrix approach. The characterisation of light-emitting one-dimensional photonic quasicrystals based on excitonic resonances is reported. The structures consist of GaAs/AlGaAs multiple quantum wells satisfying a Fibonacci sequence. The resulting band structure causes photons to become confined within the wells, where they occupy discrete quantized states. We have obtained an expression for the transmission coefficient of the Fibonacci series MQW nanostructures using analytical Transfer matrix method (ATMM) and found the resonance state within the photonic wells. These resonant states occur due to split pairs and coupling between degenerate states. The active photonic quasicrystals are good light emitters. The lack of periodicity in the Fibonacci series MQW results in resonant tunneling and strong emission. The resonant state describe here can be used to develop new types of optical devices, photonicswitching devices, detectors and optoelectronic devices.
InAs/AlSb quantum cascade lasers operating at 10 μm
InAs/AlSb intersubband quantum cascade lasers based on bound-to-continuum transitions are fabricated and operation at 10 μm is demonstrated. A spatially indirect intersubband transition together with a double plasmon waveguide structure is employed. Threshold current density is 4.9 kA/cm2 at 4 K. Temperature dependence of the threshold current density is also presented.