Enhanced luminescence of InGaN light emitting diodes with strain-compensated superlattice barriers

In this paper, we propose to use the strain-compensated Al_0.03 Ga_0.97 N/ In_0.01 Ga_0.99 N superlattices as the barrier layers within InGaN light emitting diodes (LEDs). High resolution X-ray diffraction measurements indicate good control of the interface quality for the LEDs incorporated with a strain-compensated superlattice barrier (SC-SLB). Furthermore, the thermal activation energy of the LEDs with an SC-SLB in the temperature-dependent photoluminescence (PL) measurements is estimated as about 59.9 meV, which is comparable to that of the normal LEDs. This result implies that the amount of crystalline defects, such as threading dislocation, is not significant enough to cause the deterioration of device characteristics. Because of the decrease in the strength of the piezoelectric fields within the multiple quantum wells (MQWs), the LEDs with an SC-SLB exhibit a blueshift and an increased PL intensity as compared to the normal LEDs. The lower quantum-confined Stark effect in the MQWs means that the light output power of the modified LEDs is superior to that of the normal LEDs over the entire operating range. The SC-SLB-containing LEDs also have an improved efficiency drop because the SC-SLB could provide a higher barrier height to suppress the carrier leakage.