Role of interface roughness on lateral transport in InGaN/GaN LEDs: diffusion length, dislocation spacing, and radiative efficiency

Abstract

In a LED, electrons and holes are injected from the contacts into the quantum wells. The carriers diffuse laterally in the quantum wells. In this letter, we focus on the role of interface roughness, electron-electron scattering, and dislocation scattering in the quantum well on lateral transport and present results on the diffusion length in the lateral direction. The influence of quantum well with different indium compositions, carrier densities, dislocation densities, and interface roughness are studied. A Monte Carlo simulation program is used to study the lateral mobility in quantum well. The effects of alloy scattering, charged dislocation scattering, interface roughness scattering, and e-e scattering have been included in our Monte Carlo model. The results show that the nonradiative lifetime caused by the dislocation trapping is still a dominating role for higher indium composition. This limits the internal quantum efficiency. The large interface roughness caused by a quantum dot like structures and In-clustering effect may help to improve the efficiency by reducing the diffusion length. However, our results show that for the longer wavelength source, we should try to improve the overall internal quantum efficiency first before discussing the droop effect. One is to decrease the radiative lifetime by reducing the QCSE with nonpolar/semipolar structures. The other approach would be to reduce the dislocation density to less than 10⁶<i>cm</i>^-2.