Dual stack varactor

Abstract

Embodiments include apparatuses and methods related to vertically stacked varactors. Specifically two varactors may be constructed of vertically stacked layers including an anode layer, a contact layer, and a varactor layer. The two varactors may share one or more layers in common. In some embodiments the two varactors may share the anode layer in common, while in other embodiments the two varactors may share the contact layer in common.

1 . A package comprising:
 a first varactor that includes a first contact layer, an anode layer, and a first varactor layer positioned between the first contact layer and the anode layer; and   a second varactor that resides above the first varactor and includes a second contact layer, the anode layer, and a second varactor layer positioned between the second contact layer and the anode layer, wherein:   the anode layer is positioned between the first varactor layer and the second varactor layer; and   the first varactor layer has a first doping profile, and the second varactor layer has a second doping profile, which is inverted with respect to the first doping profile.   
     
     
         2 . The package of  claim 1 , further comprising an ohmic contact coupled with the anode layer and configured to receive a negative direct current (DC) voltage. 
     
     
         3 . The package of  claim 1 , further comprising a first ohmic contact coupled with the first contact layer, and a second ohmic contact coupled with the second contact layer. 
     
     
         4 . The package of  claim 3 , wherein the first ohmic contact is a signal input, and the second ohmic contact is a signal output. 
     
     
         5 . The package of  claim 1 , wherein the first contact layer or the second contact layer is n+ doped, the first varactor layer or the second varactor layer is n− doped, and the anode layer is p+ doped. 
     
     
         6 . The package of  claim 1 , wherein the first contact layer, the second contact layer, the first varactor layer, the second varactor layer, or the anode layer include gallium, arsenic, silicon, indium, or phosphorous. 
     
     
         7 . The package of  claim 1 , wherein the anode layer includes a first anode layer directly coupled with the first varactor layer, and a second anode layer directly coupled with the second varactor layer, and an etch stop layer positioned between and directly coupled with the first anode layer and the second anode layer. 
     
     
         8 . The package of  claim 1 , wherein the second contact layer comprises a top layer directly coupled with the second varactor layer, and a bottom layer, and an etch stop layer directly coupled with and positioned between the top layer and the bottom layer. 
     
     
         9 - 16 . (canceled) 
     
     
         17 . A method comprising:
 depositing a first contact layer of a first varactor;   depositing a first varactor layer of the first varactor on the first contact layer;   depositing a common contact layer of the first varactor and a second varactor on the first varactor layer;   depositing a second varactor layer of the second varactor on the common contact layer; and   depositing a second contact layer of the second varactor on the second varactor layer, wherein the first varactor layer has a first doping profile, and the second varactor layer has a second doping profile, which is inverted with respect to the first doping profile.   
     
     
         18 . The method of  claim 17 , wherein the common contact layer is a p+ doped anode contact layer and the first contact layer and the second contact layers are n+ doped contact layers. 
     
     
         19 . The method of  claim 17 , wherein the common contact layer is an n+ doped contact layer; and wherein the first contact layer and second contact layer are p+ doped anode contact layers. 
     
     
         20 . The method of  claim 19 , further comprising:
 coupling a first signal input/output to the first contact layer;   coupling a second signal input/output to the second contact layer; and   coupling a DC voltage input to the common contact layer.   
     
     
         21 . A package comprising:
 a first varactor that includes a first contact layer, a common contact layer, and a first varactor layer positioned between the first contact layer and the common contact layer; and   a second varactor that resides above the first varactor and includes a second contact layer, the common contact layer, and a second varactor layer positioned between the second contact layer and the common contact layer;   wherein the common contact layer is positioned between the first varactor layer and the second varactor layer, the first varactor layer has a first doping profile, and the second varactor layer has a second doping profile which is inverted with respect to the first doping profile.   
     
     
         22 . The package of  claim 21 , wherein the first contact layer, the second contact layer, the first varactor layer, the second varactor layer, or the common contact layer include gallium, arsenic, silicon, indium, or phosphorous. 
     
     
         23 . The package of  claim 21 , wherein the common contact layer is a p+ doped anode contact layer and the first contact layer and the second contact layers are n+ doped contact layers. 
     
     
         24 . The package of  claim 23 , further comprising an ohmic contact coupled with the common contact layer and configured to receive a negative direct current (DC) voltage. 
     
     
         25 . The package of  claim 21 , wherein the common contact layer is an n+ doped contact layer; and
 wherein the first contact layer and second contact layer are p+ doped anode contact layers.   
     
     
         26 . The package of  claim 25 , further comprising an ohmic contact coupled with the contact layer and configured to receive a positive direct current (DC) voltage. 
     
     
         27 . The package of  claim 21 , wherein the common contact layer includes a first common contact layer directly coupled with the first varactor layer, and a second common contact layer directly coupled with the second varactor layer, and an etch stop layer positioned between and directly coupled with the first common contact layer and the second common contact layer. 
     
     
         28 . The package of  claim 21 , wherein the second contact layer comprises a top layer directly coupled with the second varactor layer, and a bottom layer, and an etch stop layer directly coupled with and positioned between the top layer and the bottom layer. 
     
     
         29 . The package of  claim 1 , wherein the first and second doping profiles are one of an abrupt profile, hyper-abrupt profile, or linear doping profile. 
     
     
         30 . The method of  claim 17 , wherein the first and second doping profiles are one of an abrupt profile, hyper-abrupt profile, or linear doping profile. 
     
     
         31 . The package of  claim 21 , wherein the first and second doping profiles are one of an abrupt profile, hyper-abrupt profile, or linear doping profile.