Strain Relaxation in Iv-vi Semiconductor Layers Grown on Silicon (100) Substrates

Abstract

ABSTRACTThe large thermal expansion coefficient mismatch between IV–VI semiconductors and silicon results in significant tensile strain when structures are cooled down following growth at high temperatures. Molecular beam epitaxy (MBE) growth of PbSe on Si (100) at 280°C on BaF2/CaF2 buffer layers results in high crack-density because of this strain. Interestingly, crack- free layers of PbSe can be grown by LPE on Si (100) by using MBE-grown PbSe/BaF2/CaF2 buffer layer structures. Unlike LPE-grown PbSe layers, however, a high crack-density was observed in Pbl-xSnxSe1-yTey layers grown by LPE on Si (100) using similar buffer layer structures. It is hypothesized that the addition of tellurium, which is known to increase IV-VI material hardness, inhibits plastic deformation and thus crack formation becomes the thermal strain relief mechanism. Ternary Pbl-xSnxSe layers grown by LPE exhibited much lower crack densities as compared to the quaternary layers and supported the conclusion that tellurium induced solid solution hardening occurs in the IV-VI materials system.