Composition-graded quantum barriers improve performance in InGaN-based laser diodes

Abstract

InGaN laser diodes (LDs) with composition-graded (CG) quantum barriers (QBs) are proposed and our study of them described. In the CG QB LDs, the indium content x in the In x Ga1-x N QB was increased gradually along the growth direction. Their laser power–current–voltage performance curves, carrier concentrations, energy band diagrams, current distributions, electrostatic fields, and stimulated recombination rate in the active region were studied. It is shown that the laser power increases from 59.8 mW to 106.9 mW at 120 mA and the slope efficiency increases from 0.76 W A−1 to 1.27 W A−1, when the conventional GaN QBs are replaced by the proposed CG QBs. The simulation results indicate that LDs with CG QBs performed better than LDs with conventional GaN QBs and InGaN QBs because the suppression of electron leakage is more efficient, as is hole injection and carrier-stimulated recombination in multiple quantum wells through the appropriate formation of polarization energy band structures.