Structural characterization of ZnSe/ZnMgSe MQWs grown on (100)GaAs by low pressure MOVPE

A detailed structural characterization of ZnSe/ZnMgSe multiple quantum wells (MQWs) grown on GaAs by low pressure metalorganic vapour phase epitaxy is presented. ZnSe/Zn0.83Mg0.17Se MQWs having between 6 and 12 periods ere deposited at 330degreesC and 304 mbar reactor pressure on( 1 0 0)GaAs after a 4.2 nm ZnSe buffer layer. The MQWs had nominal 4.4 nm thick ZnSe wells and 53 nm thick Zn(0.83)Ma(0.17)Se barriers. The MQW structural properties were investigated by high-resolution X-ray diffraction (HRXRD) and X-ray specular reflectivity (XSR) measurements, Besides the MQWs-substrate mismatch. simulation of the HRXRD and XSR patterns allowed to determine the MQW period. individual layer thickness and barrier composition. Between 8 and 10 periods the MQW structure begins to relax. its critical thickness on GaAs being between 92 and 113 nm. Furthermore. HRXRD showed broader zeroth and first-order satellite Peaks with increasing MQW periods. a result ascribed to strain fluctuations induced by either inhomogeneous Mg incorporation in the ZnSe lattice and. or interface roughening. Comparison or experimental and simulated XSR patterns allowed to determine the rms roughness at each multilayer interface, which linearly increases along the growth direction due to a cumulative intrinsic roughening.