Detection of the Interlayer at the GaAs-on-InGaP Interface in MOVPE InGaP/GaAs by the Dark Field Method

The article shows the application of (200) dark field TEM to the detection and analysis of the extra interlayer that typically forms at the GaAs-on-InGaP interface in metal organic vapour phase epitaxy (MOVPE) InGaP/ GaAs heterojunctions. Calculations of the dark field (DF) contrast function in the kinematical approximation show that the interlayer can be either GaAsP or InGaAsP for some values of the composition. Comparison with highresolution X-ray diffraction results allowed to better estimate the composition ranges of the two compounds. The possible mechanisms responsible for the formation of either GaAsP or InGaAsP are briefly discussed.