Hopping transport in the space-charge region of $p$–$n$ structures with InGaN/GaN QWs as a source of excess $1/f$ noise and efficiency droop in LEDs

It is shown that the emission efficiency and the $1/f$ noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode varies with increasing current. Analysis of the results shows that hopping transport via defect states across the $n$-type part of the space-charge region results in limitation of the current by the tunneling resistance at intermediate currents and shunting of the $n$-type barrier at high currents. The increase in the average number of tunneling electrons suppresses the $1/f$ current noise at intermediate currents. The strong growth in the density of current noise at high currents, $S_J\propto J^3$, is attributed to a decrease in the average number of tunneling electrons as the $n$-type barrier decreases in height and width with increasing forward bias. The tunneling-recombination leakage current along extended defects grows faster than the tunneling injection current, which leads to emission efficiency droop.