Strain relaxation in IV-VI semiconductor layers grown on silicon (100) substrates

摘要

The 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 deg C on BaF_2/CaF_2 buffer layers results in high crack-density because of this strain. Interestingly, crackfree layers of PbSe can be grown by LPE on Si (100) by using MBE-grown PbSe/BaF_2/CaF_2 buffer layer structures. Unlike LPE-grown PbSe layers, however, a high crack-density was observed in Pb_(1-x)Sn_xSe_(1-y)Te_y 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. Tenary Pb_(1-x)Sn_xSe 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.