Effect of substrate temperature on optical properties and strain distribution of ZnTe epilayer on (100) GaAs substrates

Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

“…The reason for this is not clear now, but it may be due to the different acceptors for these two structures, or due to the tensile strain in the ZnTe epilayer induced by the lattice mismatch and the difference in thermal expansion coefficient between the GaAs substrate and the ZnTe epilayer. [5,23] All of these results show that both the ZnTe epilayer and the ZnTe bulk crystal used in this work are of good structural quality, due to the sharp bound excitonic emission I a and the absence of deep structural defect-related Y lines. Furthermore, although the excitonic emissions (I a and FE) from the ZnTe epilayer are somewhat weaker than that from the ZnTe bulk crystal, which may be due to As atoms diffusing into the ZnTe epilayer and/or because of the strain-induced degradation of crystalline quality of the ZnTe epilayer, the DAP and e-A emissions, which are observed in the ZnTe bulk crystal in this work or are often observed in the ZnTe bulk crystal and ZnTe homoepitaxial layers in other studies, [26,27] do not appear in the ZnTe epilayer, indicating that the ZnTe epilayer grown on its GaAs substrate is a promising material or structure for applications in future optoelectronic devices.…”

“…The energy redshift could be attributed to the increase in strain with the increase of the effective excited depth in the ZnTe epilayer. [22,23] In fact, in previous work, [5] it has been found that the energy of the I a peak increases monotonically with increasing ZnTe epilayer thickness, suggesting that a tensile strain existing in ZnTe/GaAs epilayer can be gradually relaxed with increasing the ZnTe epilayer thickness. transition of the excitons bound to the As atoms (or As-related complex) diffusing from the GaAs substrate into the epilayer during the growth of the epilayer, due to the high growth temperatures.…”