Threshold Base Current and Light Power Output of Symmetric and Asymmetric Multiple Quantum-Well Transistor Lasers

We have developed by solving continuity equation the expressions for the terminal currents of Transistor Lasers that incorporate Multiple Quantum Wells in the base. The bulk carrier density in base is related with the two-dimensional carrier density in QWs via virtual states. Strain, 2D density-of-states, polarization dependent momentum matrix element, Fermi statistics and Lorentzian broadening are considered to estimate the QW gain. Comparison between the calculated and experiment values indicates substantial reduction in threshold base current for symmetric MQW-TL having equal QW and barrier widths. Calculations are also made for three QWs of different widths having variable barrier widths (Asymmetric MQW-TL). Reduction of threshold base current by different amounts is observed in all cases.