Self-consistent Solution Of Schrodinger-Poisson Equations Research Articles

Temperature performance analysis of intersubband Raman laser in quantum cascade structures

In this paper we investigate the effects of temperature on the output characteristics of the intersubband Raman laser (RL) that integrated monolithically with a quantum cascade (QC) laser as an intracavity optical pump. The laser bandstructure is calculated by a self-consistent solution of Schrodinger-Poisson equations, and the employed physical model of carrier transport is based on a five-level carrier scattering rates; a two-level rate equations for the pump laser and a three-level scattering rates to include the stimulated Raman process in the RL. The temperature dependency of the relevant physical effects such as thermal broadening of the intersubband transitions (ISTs), thermally activated phonon emission lifetimes, and thermal backfilling of the final lasing state of the Raman process from the injector are included in the model. Using the presented model, the steady-state, small-signal modulation response and transient device characteristics are investigated for a range of sink temperatures (80–220K). It is found that the main characteristics of the device such as output power, threshold current, Raman modal gain, turn-on delay time and 3-dB optical bandwidth are remarkably affected by the temperature.

A Versatile Physics-Based Circuit Model for Mid-Infrared Quantum Cascade Lasers

In this paper, we present a comprehensive circuit-level model that accounts for the thermal and bias dependence of a quantum cascade (QC) laser's behavior. The equivalent circuit model of laser by employing a number of quantum mechanical models such as the coherent transport, simplified four-level carrier scattering rates, and heat transfer equation is developed. The total equivalent circuit is composed of input circuit coupled to intrinsic QC circuit and thermal circuit which models the behaviors of each component and whole device. In the model, to take into account the field dependence of the circuit parameters including the detuning and energy levels, backfilling excitation energy, and escape activation energy, the extraction of parameters has been performed as fitted functions by a self-consistent solution of Schrodinger-Poisson equations for a wide range of applied electric fields. The presented model is used to investigate the static and dynamic performances of QC laser operating in the mid-infrared (Mid-IR). For a typical Mid-IR QC laser, a good agreement was found for the temperature-dependent light output-current characteristics.

Low thermal drift in highly sensitive doped channel Al0.3Ga0.7As/GaAs/In0.2Ga0.8As micro-Hall element

Micro-Hall sensors with high sensitivity, low noise, and high thermal stability, 5 μm square, are fabricated using pseudomorphic Al0.3Ga0.7As/GaAs/InyGa1-yAs (0.2 ≤ y ≤ 0.3) heterostructures with Si-doped channels. The structures were optimized for thermal stability using a calculation of the self-consistent solution of Schrodinger-Poisson equations and Fermi-Dirac statistics in Hartree approximation. The optimized structure based on a Si-δ-doped 144 A In0.2Ga0.8As quantum well embedded into uniformly doped GaAs channel showed thermal drifts of only 90 ppm·K−1 in current drive mode and 192 ppm K−1 in voltage drive mode. The measurements of the absolute magnetic sensitivity and the low frequency noise were done. The micro-Hall sensor, optimized for thermal drift, is able to resolve the magnetic field of 438 nT.

Investigation of the recombination dynamics in low In‐content InGaN MQWs by means of cathodoluminescence and photoluminescence excitation

In this work we present a detailed optical characterization of InGaN-based multiple QWs performed by combining time-resolved and time-integrated photoluminescence and cathodoluminescence techniques. The experimental results are well reproduced in the framework of a theoretical model where a self-consistent solution of Schrodinger-Poisson equations is coupled to a rate equation model to account for time-dependent effects of charge re-arrangement to determine the electronic states in the nanostructure. The theoretical model is demonstrated to describe in a common scenario either time-integrated and time dependent photoluminescence and finally cathodoluminescence, for samples having different well widths (i.e. different internal polarization fields). We demonstrate that, provided the correct material parameters of the InGaN/GaN alloys are considered in the model, including the bowing of the polarization fields and gap, the same theoretical approach previously reported for AlGaN/GaN systems applies. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)