Formula omitted] ratio dependence of surface macrodefects in CdTe/ZnTe/GaAs(100) growth by metalorganic vapor phase epitaxy

Abstract

We studied the surface morphology of CdTe(100) layers on GaAs(100) by metalorganic vapor phase epitaxy (MOVPE). When CdTe(100) layers were obtained using thin ZnTe nucleation layers, we observed high-density pyramidal macrodefects, known as hillocks, in the epilayer surface. We found the density of hillocks to be strongly dependent on the VI II ratio during both ZnTe and CdTe growth processes. We optimized both the Te Zn and Te Cd ratios to obtain a minimum hillock density of 1 × 10 2 cm −2. These results show that hillocks were nucleated at both the epilayer/substrate and CdTe ZnTe interfaces. By X-ray diffraction measurement, we confirmed that the quality of the crystal structural was also good under this condition. We also found the initial nucleation conditions to be more important for the structural quality. In (100)HgCdTe/CdTe/GaAs growth, pyramidal hillocks on the CdTe buffer surface caused substantial (> 100 μm) macrodefects in HgCdTe layers, which were fatal for infrared devices. Their shape was enlarged especially in one direction. To achieve a low density of surface macrodefects in HgCdTe(100) or CdTe(100) layers on GaAs(100) substrates, we need to precisely control the VI II ratio.