In these proceedings, we present the analyses of single electrons from semileptonic decays of open heavy flavor hadrons at mid-rapidity in p+p and Au+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV. The data for Au+Au collisions were taken with the Heavy Flavor Tracker which enables a topological separation of electrons originating from bottom- and charm-hadron decays. We report results on the fraction of bottom-decayed electrons as a function of transverse momentum for Au+Au collisions from the STAR experiment with significantly improved precision compared to previous measurements. At the same time, improved measurements of nuclear modification factors ($R_{\rm AA}$) of bottom- and charm-decayed electrons and a new measurement of the double ratio of $R_{\rm CP}$ between bottom- and charm-decayed electrons are also be presented.