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The Effect of the Carrier Drift Velocity Saturation in High-Power Semiconductor Lasers at Ultrahigh Drive Currents

Experimental light–current characteristics of high-power semiconductor lasers operating at ultrahigh drive currents have been studied in terms of numerical models taking into account the effect of the carrier drift velocity saturation. It was shown that the simplest diffusion–drift (DD) model underestimates the optical loss at high drive currents, which leads to overestimation of the peak optical power when compared with the experimental results. The inclusion of the carrier drift velocity saturation effect into the DD model results in that a strong-electric-field domain is formed at the interface with the active region on the side of the p-emitter already at low drive currents. The amplitude of this field substantially grows as the current increases further, which restricts application of this model to description of high-power semiconductor lasers at high drive currents. With the nonlocal energy-balance model used to describe the carrier transport in the laser heterostructure, it becomes possible to take into account the effect of carrier heating by the electric field. As a result of the carrier heating, the drift velocity decreases and the concentration of excess carriers in the waveguide layer grows, compared with the simplest DD model. The inclusion of the additional internal optical loss mechanism obtained in the energy-balance model provided a satisfactory coincidence of the calculated light–current characteristics with the experimental dependences.