In　this　paper　the　limit　of　vanishing　Debye　length　in　a　bipolar　drift-diffusion　model　for　semiconductors　with　physical　contact-insulating　boundary　conditions　is　studied　in　one-dimensional　case.　The　quasi-neutral　limit　(zero-Debye-length　limit)　is　proved　by　using　the　asymptotic　expansion　methods　of　singular　perturbation　theory　and　the　classical　energy　methods.　Our　results　imply　that　one　kind　of　the　new　and　interesting　phenomena　in　semiconductor　physics　occurs.　(C)　2010　Elsevier　Inc.　All　rights　reserved.