Opposite change trend of electrical behavior curves near the threshold between GaAs- and GaN-multi-quantum-well laser diodes

The opposite and abrupt change trends of the electrical behavior between narrow and wide bang-gap multi-quantum-well (MQW) laser diodes (LDs) in the ‘threshold region’, which corresponds to the current region between two kinks in the I d V /d I – I curves, were confirmed from the apparent properties measured directly and junction properties extracted by our ac-IV method, as well as simulation calculations. In the threshold region, negative capacitance and series resistance curves in narrow bandgap LDs (wavelengths are 780 and 650 nm) drop down, while in wide-bandgap LDs (wavelengths are 450 and 405 nm), they jump up; the junction voltage curves in narrow bandgap LDs jump up, while in wide-bandgap LDs, they drop down. We qualitatively interpreted the opposite change trend of these electrical parameters, and concluded that different stimulated emission mechanisms caused this opposite change trend of LDs with these two types of materials.