Exciton recombination in lasing contributing an opposite abrupt change of the electrical behavior near threshold between GaN- and GaAs- multi-quantum-well laser diodes

The opposite sudden change of electrical characteristics between narrow and wide bang-gap multi-quantum-well (MQW) laser diodes (LDs) in the threshold region (which is defined as a current region between two kinks of IdV/dI–I curve) shows an interesting phenomenon that the slope changes of IdV/dI–I or V j –I curve between two adjacent regions ('below' and 'in', or 'in' and 'above' threshold region) display an approximate e-exponential relationship with the wavelengths of LDs. After comparing the exciton binding energy in different MQW LDs, and analyzing the temperature dependence of V j –I and IdV/dI–I of GaN MQW LDs, we suggested that the fraction of exciton recombination into lasing is a reason causing the relationship of sudden changes of the electrical characteristics with wavelengths of LDs.