Measurements of TiOx stress induced on InP/InGaAs/InGaAsP quantum well heterostructures

Abstract

Measurements of stress induced by TiO_x layers on single quantum well InP based heterostructure are presented. Strain characterization has been performed by photoluminescence (PL) and micro-Raman spectroscopy. We present a comparison of the stress induced by TiO_x and SiO₂ layers which are commonly used as masking material for the quantum well intermixing process. Micro-Raman spectroscopy and PL revealed that TiO₂ is creating a stress field in the top layers of the heterostructure, with a dependence on temperature and stressor thickness. A hysteresis phenomenon of the Raman shift has also been observed after measurements at low temperature (below 300 K) which shows that the stress created by TiO_x exceeds the elastic limit of InP. On the other hand, there is no evidence that SiO₂ is inducing stress. Rapid thermal annealing of samples covered with titanium oxide results in improvement of the thermal stability.