Effect of in-situ Zn doping on suppression of phase separation in InxAl1-xAs epitaxial layer on InP(001) grown by MOCVD

The effect of Zn impurities on the surface morphology evolution and phase separation behavior of the InAlAs layer on InP(001) substrates is investigated using metal organic chemical vapor deposition (MOCVD). The phase separation of InAlAs occurs at a relatively low growth temperature (T < 620 degrees C), accompanied by surface roughening and bandgap lowering. According to the microstructural analyses, indium (In) and aluminum (Al) atoms have high reactivity with In-rich or Al-rich columns in a certain growth region. The addition of Zn impurities during InAlAs growth at the phase-separating temperature results in the suppression of phase separation, which can be attributed to a high probability of Zn incorporation into the sites, which generates an In-rich and Al-rich phase column in the phase-separated InAlAs layer. Based on atomic force microscopy (AFM) and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) analysis, we classify four types of InAlAs surface morphology as a function of the growth temperature and flow rate of Zn impurities.