Combined (200) DF-TEM and X-ray diffraction investigations of interfacesin MOVPE grown InGaP/GaAs heterojunctions

The presence of interlayers at the inverted GaAs-on-InGaP interfaces in MOVPE grown InxGa1-xP/GaAs heterojunctions has been evidenced by (200) dark field (DF) transmission electron microscopy and high resolution X-ray diffraction. A relatively large negative strain is associated with the interlayers. Analysis of the kinematical DF contrast has allowed to establish which kind of InxGa1-xAs1-yPy compound the interlayer can be made of and the possible ranges for the compositions x and y. The localization of the interlayer at the bottom of the GaAs layer and inside it would suggest that its formation can be due to the incorporation into GaAs of P atoms remained in the reactor after PH3 was switched off and In carry-over.