Analytical Modeling of Tunnel-Junction Transistor Lasers

Compared with transistor lasers (TLs), tunnel-junction transistor lasers (TJTLs) are more easily modulated with the voltage across base-collector (BC) junction. In this work, the charge-control model and modified rate equation of TJTLs which includes the Franz-Keldysh effect and direct tunneling is developed. We conduct DC and AC analysis with our model and show that the doping concentration in the BC junction plays a key role in the capability to voltage modulate TJTLs since it affects the junction field. A trade-off between the optical power and capability of the voltage modulation emerges as a concern for designing the doping concentration. We also study the effect of the quantum well (QW) position. The result shows that the QW closer to the BC junction can obtain a higher confinement factor to achieve better output power and modulation bandwidth.