Comparative study of the differential resistance of GaAs- and GaN-based laser diodes

The differential resistance curves of GaAs- and GaN-based laser diodes (LDs) are experimentally and numerically investigated. It is found that the dependence of the differential resistance upon the injection current differs in the GaAs- and GaN-based LDs mainly in two aspects. The first is the kink polarity of the differential resistance in the vicinity of the threshold current, and the second is the behavior of the differential resistance curve beyond the threshold current. Self-consistent calculation results suggest that the LD kink and its polarity are determined by the superposition effects of the n-side, active and p-side regions of LDs. It is found that this kink mainly differs in the differential resistance curves of the active region, while the difference in the behavior of the differential resistance curve after the lasing threshold is ascribed to a resistance change in the p-side region caused by a reduced ideality factor.