Radiation detectors can be made of n-type or p-type silicon. All segmented detectors on p-type silicon and double-sided detectors on n-type silicon require an “inter-segment isolation” to separate the n-type strips from each other; an alumina layer for isolating the strip detectors is applied, and forms negative charges at the silicon interface with appropriate densities. When alumina dielectric is deposited on silicon, the negative interface charge acts like an effective p-stop or p-spray barrier because electrons are “pushed” away from the interface due to the negative interface charge.