Doped Semiconductor Nanocrystal Layers And Preparation Thereof

Abstract

The present invention relates to a doped semiconductor nanocrystal layer comprising (a) a group IV oxide layer which is free of ion implantation damage, (b) from 30 to 50 atomic percent of a semiconductor nanocrystal distributed in the group IV oxide layer, and (c) from 0.5 to 15 atomic percent of one or more rare earth element, the one or more rare earth element being (i) dispersed on the surface of the semiconductor nanocrystal and (ii) distributed substantially equally through the thickness of the group IV oxide layer. The present invention also relates to a semiconductor structure comprising the above semiconductor nanocrystal layer and to processes for preparing the semiconductor nanocrystal layer.

1 - 45 . (canceled)  
     
     
         46 . A process for preparing a doped semiconductor nanocrystal layer, the process comprising: 
 (a) introducing (i) a gaseous mixture of a group IV element precursor and molecular oxygen, and (ii) a gaseous rare earth element precursor, at the same time in a plasma stream of a Plasma Enhanced chemical Vapor Deposition (PECVD) instrument, whereby the rare earth element and the group IV element are deposited onto a substrate simultaneously to form a semiconductor rich group IV oxide layer doped with a rare earth element, and    (b) annealing the semiconductor rich group IV oxide layer doped with a rare earth element at a temperature of from 600° C. to 1000° C., whereby atomic excess of the group IV element is converted into semiconductor nanocrystals; and    whereby the rare earth elements are dispersed through the semiconductor rich group IV oxide layer when the semiconductor nanocrystals are formed, and    whereby the rare earth elements are localized on the surface of the nanocrystals.    
     
     
         47 . A process according to  claim 46 , wherein the group IV element precursor is a hydride of a group IV element.  
     
     
         48 . A process according to  claim 46 , wherein the group IV element precursor comprises silicon, germanium, tin or lead.  
     
     
         49 . A process according to  claim 46 , wherein the group IV element precursor is silane.  
     
     
         50 . A process according to  claim 46 , wherein the ratio of the group IV element precursor and of the molecular oxygen is selected to obtain the semiconductor rich group IV oxide layer with 30 to 50 atomic percent of excess semiconductor.  
     
     
         51 . A process according to  claim 46 , wherein the rare earth element precursor comprises a rare earth element selected from cerium, praseodymium, neodymium, promethium, gadolinium, erbium, thulium, ytterbium, samarium, dysprosium, terbium, europium, holmium, lutetium, and thorium.  
     
     
         52 . A process according to  claim 46 , wherein the rare earth element precursor comprises erbium, thulium or europium.  
     
     
         53 . A process according to  claim 46 , wherein the rare earth element precursor comprises a ligand selected from 2,2,6,6-tetramethyl-3,5-heptan-edione, acetylacetonate, flurolacetonate, 6,6,7,7,8,8,8-heptafluoro-2,2-di-methyl-3,5-octanedione, i-propylcyclopentadienyl, cyclopentadienyl, and n-butylcyclopentadienyl; whereby the rare earth element precursor with the ligand forms a compound, which is volatile and enters the gaseous phase at a relatively low temperature without changing the chemical nature of the compound, and comprises organic components that, upon exposure to the plasma in the PECVD apparatus, will form gaseous by-products that can be removed through gas flow or by reducing the pressure within the PECVD apparatus.  
     
     
         54 . A process according to  claim 46 , wherein the rare earth element precursor is selected from tris(2,2,6,6-tetramethyl-3,5-heptanedionato) erbium(III), erbium (III) acetylacetonate hydrate, erbium (III) flurolacetonate, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedi-onate)erbium (III), tris(i-propylcyclopentadienyl)erbium (III), Tris(cyclopentadienyl)erbium (III), and tris(n-butylcyclopentadienyl)erbi-um (III).  
     
     
         55 . A process according to  claim 46 , wherein the semiconductor rich group IV oxide layer is annealed at a temperature of from 800 to 950° C.  
     
     
         56 . (canceled)  
     
     
         57 . The process according to  claim 46 , wherein step (b) is carried out under an oxygen atmosphere to insure oxidation of the rare earth element, or under a reduced pressure in order to facilitate the removal of any volatile by-products that are produced.  
     
     
         58 . The process according to  claim 46 , further comprising heating the rare earth element precursor to ensure it is in a gaseous state.  
     
     
         59 . The process according to  claim 58 , wherein the rare earth element precursor is heated in an oven at between 80° C. and 110° C.  
     
     
         60 . The process according to  claim 46 , wherein the gaseous rare earth element precursor is introduced to the plasma stream with an inert carrier gas.  
     
     
         61 . The process according to  claim 46 , wherein the gaseous rare earth element precursor is introduced to the plasma at a position that is below a position where the group IV element containing compound is introduced to the plasma.  
     
     
         62 . The process according to  claim 46 , wherein step a) includes use of a dispersion ring to assist in the dispersion of the gaseous rare earth element precursor in the plasma.  
     
     
         63 . The process according to  claim 46 , wherein step a) includes placing the substrate on a rotating scepter to obtain a more even deposition of the semiconductor rich group IV oxide layer.  
     
     
         64 . The process according to  claim 46 , further comprising producing the plasma in an Electron Cyclotron Resonated (ECR) reactor, wherein electrons have a spiral motion caused by a magnetic field, which allows a high density of ions in a low-pressure region, whereby a rare earth metal component of the rare earth element precursor is stripped of organic components of the rare earth element precursor and incorporated uniformly and in a high concentration.