Superlattice quantum well infrared detector having exposed layers

Abstract

In at least one embodiment, an infrared (IR) detector is provided. The IR detector comprises a thermal sensing element that includes an absorber that is formed of a superlattice quantum well structure. The superlattice quantum well structure includes a first layer and a second layer, the first layer being arranged to extend in a first plane and the second layer being positioned proximate to the first layer and extending in the first plane. The second layer extending further than the first layer in the first plane such that a portion thereof is exposed for receiving a conductive material to increase electrical conductivity in the detector.

1 . An infrared (IR) detector comprising:
 a thermal sensing element including an absorber that is formed of a superlattice quantum well structure, the superlattice quantum well structure including:
 a first layer for extending in a first plane; and 
 a second layer being positioned proximate to the first layer and extending in the first plane, wherein the second layer extends further than the first layer in the first plane such that a portion thereof is exposed for receiving a conductive electrical material to increase electrical conductivity in the detector. 
   
     
     
         2 . The detector of  claim 1  wherein the first layer comprises silicon and the second layer comprises silicon germanium. 
     
     
         3 . The detector of  claim 2  wherein the first layer of silicon and the second layer of silicon each has a thickness of generally 100 angstroms. 
     
     
         4 . The detector of  claim 1  wherein the first layer is one of a plurality of barrier layers and the second layer is one of a plurality of conducting layers, each of the barrier layers and the conducting layers being arranged to alternate with one another. 
     
     
         5 . The detector of  claim 4  wherein the plurality of barrier layers and the plurality of conducting layers has a total thickness of generally 1000 angstroms. 
     
     
         6 . The detector of  claim 4  further comprising a first encapsulation layer and a second encapsulation layer, the plurality of barrier layers and the plurality of conductive layers being positioned between the first and the second encapsulation layers. 
     
     
         7 . The detector of  claim 5  wherein each of the first and the second encapsulation layers comprise one of silicon nitride and silicon dioxide. 
     
     
         8 . The detector of  claim 1  wherein the detector further comprises a first arm positioned on a first side of the absorber and a second arm positioned on a second side of the absorber, wherein the first arm and the second arm are each formed of the superlattice quantum well structure such that the absorber is thermally isolated by the first arm and the second arm. 
     
     
         9 . The detector of  claim 8  wherein at least one of the first arm and the second arm includes a third layer for extending in the first plane and a fourth layer for extending in the first plane, the fourth layer being arranged to extend further in the first plane such that a portion thereof is exposed for receiving the conductive material to increase electrical conductivity with the absorber. 
     
     
         10 . The detector of  claim 9  wherein the third layer comprises silicon and the fourth layer comprises silicon germanium. 
     
     
         11 . The detector of  claim 10  wherein the silicon germanium is one of n-type doped and p-type doped, and wherein the doping concentration of the silicon germanium is between 5×10 18  and 5×10 19  atoms/cm 3 . 
     
     
         12 . An infrared (IR) detector comprising:
 a thermal sensing element including an absorber and an arm, the absorber being electrically connected to the arm, and each of the absorber and the arm including:
 a first layer for extending in a first plane; and 
 a second layer being positioned proximate to the first layer and extending in the first plane, wherein the second layer extends further than the first layer in the first plane such that a portion thereof is exposed for receiving a conductive electrical material to increase electrical conductivity in the detector. 
   
     
     
         13 . The detector of  claim 12  wherein the each of the absorber and the arm are formed of a superlattice quantum well material. 
     
     
         14 . The detector of  claim 13  wherein the first layer comprises silicon and the second layers comprises silicon germanium. 
     
     
         15 . The detector of  claim 14  wherein the first layer of silicon and the second layer of silicon germanium each has a thickness of generally 100 angstroms. 
     
     
         16 . The detector of  claim 12  wherein the first layer is one of a plurality of barrier layers and the second layer is on a plurality of conducting layers, each of the barrier layers and the conducting layers being arranged to alternate with one another. 
     
     
         17 . The detector of  claim 16  wherein the plurality of barrier layers and the plurality of conducting layers has a total thickness of generally 1000 angstroms. 
     
     
         18 . The detector of  claim 16  further comprising a first encapsulation layer and a second encapsulation layer, the plurality of barrier layers and the plurality of conductive layers being positioned between the first and the second encapsulation layers. 
     
     
         19 . A method of forming an infrared (IR) detector, the method comprising:
 forming an absorber with at least one first layer and at least one second layer having a superlattice quantum well structure; and   etching exposed sections in the at least one first layer and the at least one second layer with a binary mask operation such the exposed sections receive conductive electrical material to increase electrical conductivity in the detector.   
     
     
         20 . The method of  claim 19  wherein a total number of exposed sections of the at least one first layer and the at least one second layer is equal to 2 N , where N is the number of masks. 
     
     
         21 . The method of  claim 19  wherein N is equal to 3 such that 8 exposed sections are formed.