Influence of Heterointerface Abruptness on Electrorefractive Effect in InGaAs/InAlAs Five-Layer Asymmetric Coupled Quantum Well

An InGaAs/InAlAs five layer asymmetric coupled quantum well (FACQW) is expected to produce a large electrorefractive index change and is a promising structure for high-performance phase modulators. However, because an FACQW is composed of ultrathin layers, poor abruptness in heterointerface may deteriorate the electrorefractive effect. We therefore investigated theoretically the influence of abruptness of heterointerfaces in an FACQW on the electrorefractive effect of the FACQW. In the analysis, it is assumed that the composition profile in a heterointerface is exponential, and the thickness of the transition layer L is defined. With the increase in L, the absorption edge is blue-shifted, which deteriorates the electrorefractive index change of the FACQW especially in the case of L >= 3 monolayer (ML). In addition, we propose an improved FACQW structure, which is expected to exhibit a large electrorefractive index even in the case of L = 3 ML. (C) 2010 The Japan Society of Applied Physics