Reduced nonthermal rollover of wide-well GaInN light-emitting diodes

Nonthermal rollover (or efficiency droop) of the electroluminescence (EL) efficiency has been investigated for near-UV-emitting (AlGaIn)N single-well light-emitting diodes (LED) with varying GaInN well widths grown on substrates with different dislocation densities (DDs). For each DD the well width of the mesa-LEDs has been optimized for maximum EL efficiency at high operating currents. LEDs on freestanding GaN (DD 4×107 cm−2) with an 18 nm thick GaInN wide-well active region show the highest efficiency, and the output power-versus-current characteristic remains linear up to the highest pulsed current density of 750 A/cm2. In contrast, LEDs on sapphire grown with conventional low-temperature nucleation (DD 109 cm−2) exhibit the optimum well width at 3 nm and show significant nonthermal rollover.