Small-Signal Equivalent-Circuit Model and Characterization of 1.55-μm Buried Tunnel Junction Vertical-Cavity Surface-Emitting Lasers

An equivalent-circuit model for a novel 1.55- μm buried tunnel junction vertical-cavity surface-emitting laser chip is proposed based on the structure of the device. The values of the equivalent-circuit elements are determined by fitting the reflection and transmission coefficients at different bias currents. Good agreement between measured and simulated results implies the validity of the equivalent-circuit model. The influences of the buried tunnel junction, active region, and parasitic parameters on the high-frequency responses are investigated based on measurements and theoretical predictions. It is shown that the impedance of the device will change with the bias current, even if the bias current is above threshold, which is different from the edge-emitting laser, and the frequency responses depend on both the buried tunnel junction and mesa diameters.