Blue-green semiconductor lasers are potentially important in high density optical recording and full color displays. The device lifetime is still unacceptably short, and early degradation has been related to stacking faults at II-VI/III-V interfaces, and to the dissipation at contacts that derives from doping limitations. However, little information exists on the effect of the substrate orientation, step density, and initial II-VI growth conditions on the structural and electronic parameters of the final interface, and on dopant incorporation and self-compensation. We will explore this connection with a range of experimental techniques. In particular, we will examine the effect of substrate orientation (vicinal as well as high index surfaces) and Zn/Se beam pressure ratio on the stacking fault density at II-VI/III-V heterojunctions, and on the maximum net carrier density achievable in bulk and delta-doped p-type and n-type II-VI epilayers grown by molecular beam epitaxy on GaAs and InGaAs substrates.