Silicon light emitting device and a method of making the device

DETAILED DESCRIPTION OF THE INVENTION Referring to the Figures, a light emitting device 10 comprises a substrate 12 having first and second major surfaces 14 and 16 respectively; a region 18 of opposite conductivity type to that of the substrate 12 extends a distance into the substrate 12 from the major surface 14 thereby forming a p-n junction at the interface 20 between the regions of opposite conductivity type; a region 22 extending about the p-n junction contains lattice defects and hydrogen; an electrically insulating layer 24 overlies a portion of the major surface 14 of the substrate 12; electrical contact is made to the substrate 12 by means of an electrically conducting layer 26 which contacts the substrate through an opening in the electrically insulating layer 24; electrical contact is made to the region 18 of opposite conductivity type to that of the substrate 12 by an electrically conducting layer 28 which contacts the region 18 through an opening in the electrically insulating layer 24; and a light reflecting layer 30 which overlies the second major surface 16 of the substrate 12.
Referring to FIG.
2, the identification of the elements common to the light emitting device 40 and the light emitting device 10 of FIG.
1 is the same.
The light emitting device 40 differs in that the region of opposite conductivity type 18 is a layer which overlies the surface 14 of the substrate 12 and in that the light reflecting layer 30 also serves as the electrical contact to the substrate.
The substrate 12 is composed of a body of crystalline silicon which may be of either n- or p-type conductivity and which has a resistivity between about 0.
1 ohm-cm and about 50 ohm-cm.
Typically, the substrate has a resistivity of about 10 ohm-cm.
The region 18 of opposite conductivity type may be formed either by diffusion or implantation of an appropriate dopant into the surface 14 of the substrate 12 or may be formed as a layer on the surface 14 of the substrate 12 using epitaxial growth techniques.
The electrically insulating layer 24, composed of a material such as silicon dioxide, having an opening therein may serve as a mask to restrict the diffusion or implantation to only a portion of the major surface 14