The effect of active layer design on the efficiency of InGaN light emitting diodes (LEDs) with the light emission in blue
(~420 nm) has been studied. Correlation between the internal quantum efficiency (IQE) and relative external quantum
efficiency (EQE) and salient features of structures on c-plane InGaN LEDs which contain multiple quantum wells
(MQWs) of different barrier height (either In<sub>0.01</sub>Ga<sub>0.99</sub>N or In<sub>0.06</sub>Ga<sub>0.94</sub>N barriers) and thickness (3 nm and 12 nm) as well
as different double heterostructure (DH) designs (3 nm, dual 3 nm, 6 nm, dual 6 nm, 9 nm and 11 nm) with inserted 3
nm In<sub>0.06</sub>Ga<sub>0.94</sub>N barrier. Pulsed electroluminescence (EL) and optical excitation power-dependent photoluminescence
(PL) measurements indicated that the thinner and lower In<sub>0.06</sub>Ga<sub>0.94</sub>N barriers bode well for high EQE and IQE.
Furthermore, increase of the effective active region thickness by multiple InGaN DH structures (dual, quad and hex)
separated by 3 nm In<sub>0.06</sub>Ga<sub>0.94</sub>N barriers is promising at high injection levels. Although increasing the single DH
thickness from 3 to 6 nm improves the peak relative EQE by nearly 3.6 times due to increased density of states and
increased emitting volume, the IQE suffers a nearly 30% loss. Further increase in the DH thickness to 9 and 11 nm
results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably
due to degradation of the InGaN layer. Increasing the number of 3 nm DH active regions with 3 nm In<sub>0.06</sub>Ga<sub>0.94</sub>N
barriers improves EQE, while still maintaining high IQE (above 95% at a carrier concentration of 10<sup>18</sup> cm<sup>-3</sup>) and
showing negligible EQE degradation up to 550 A/cm<sup>2</sup> due to increased emitting volume and high radiative
recombination coefficients and high IQE.