Formation of CdTe columnar structures prompted by In- and Ga-rich nanodots

The vapor-phase epitaxy (VPE) deposition of CdTe on III-V heterosubstrates was performed in order to investigate the formation of micro-pixels usable in X-ray and thermo-photovoltaic converters. InSb and (Ga)InSb layers grown by molecular beam epitaxy on semi-insulating GaAs (1 0 0) wafers were employed as substrates. In these layers, the presence of Ga- and In-rich dots (200-500 nm in diameter) was detected using AFM and SEM-EDAX techniques. We found that these dots, which are in liquid phase at the VPE growth temperature (450 °C), act as nucleation points during the VPE process and prompt the selective area deposition of CdTe leading to the formation of columnar structures. Two important trends related to the growth morphology were established. First, the group V element does not affect the growth of CdTe columnar structures, i.e. the formation of these structures is independent of As or Sb. Second, the In-rich dots prompt the formation of CdTe columnar structures than the Ga-rich dots better.