Semiconductor device

Abstract

A semiconductor structure is provided comprising a bulk substrate of semiconductor material having a first-type doping conductivity in a first dopant concentration. A first layer of semiconductor material is epitaxially formed on the substrate, such first layer having the first-type doping conductivity in a second dopant concentration lower than the first concentration. A second layer of semiconductor material is epitaxially formed on the first layer, the second layer having a second-type doping conductivity opposite to the first-type doping conductvity and thereby forming a P-N junction with the first layer. A plurality of regions, comprising semiconductor material having the first-type doping conductivity and extending through the second layer and a predetermined distance into the first layer, are further included for providing electrical isolation between active devices formed in different regions of the second layer. The thickness of the first layer is selected to be greater than the diffusion lengths of electron-hole pairs emitted by the bulk substrate in response to incident radiation and smaller than the thickness of the bulk substrate. With such arrangement, electron-hole pairs emitted by the substrate are substantially prevented from reaching such P-N junction, and few electron-hole pairs are emitted by the first layer, due to the small thickness thereof. Thus, electron-hole current at such P-N junction is reduced, thereby decreasing the effects of incident radiation on active devices formed in the semiconductor structure.