Inhomogeneous carrier distribution in InGaN multiple quantum wells and its influences on device performances

摘要

We investigate the effect of carrier distribution characteristics in InGaN multiple-quantum-well (MQW) structures on the efficiency droop of light-emitting diodes (LEDs). Here, three kinds of inhomogeneous carrier distributions are studied; inhomogeneous carrier distribution in the vertical direction between QWs, that in the horizontal direction of a QW plane due to the current crowding in the LED chip, and that inside QW materials by carrier localization in the In-rich areas. It is found, by numerical simulation, that the built-in polarization field in InGaN MQWs makes the hole distribution between QWs more inhomogeneous, which enhances the efficiency droop. In addition, nonuniform current spreading is also found to have a significant influence on the efficiency droop by the inhomogenous carrier distribution in the plane of a QW. When the carrier distribution characteristic is investigated in a microscopic scale, the localization of carriers in the In-rich areas is expected to reduce the effective active volume where carriers are able to recombine, and enhances the efficiency droop due to the large increase in the carrier density at inhomogeneously distributed In-rich regions.