Imbalanced Carrier and Photon Density Distribution in Multiple Quantum Well Transistor Laser

In this paper we present a large signal analysis for the Heterojunction Bipolar Transistor Laser (HBTL) to reveal its optical behavior under high current injection conditions. Physical structure of the device studied here, is based on npn HBT (n-InGaP/p-GaAs+InGaAs(quantum wells)/n-GaAs) .Utilizing appropriate models for carrier transport, nonlinear optical gain and optical confinement factor (OCF), we have simulated the large signal response of the HBTL in relatively low and high modulation frequencies. Our results predict that for multiple quantum well structures at low frequencies there should not be a difference in carrier density neither the photon density. However, carrier concentration can be differently distributed between subsequent wells in case of a high speed yet large signal input. This leads to increased linewidth instead as it depends on carrier density difference between first and last quantum wells ({Delta}Nqw).