Semiconductor diodes with low reverse bias currents

Abstract

A diode is described with a III-N material structure, an electrically conductive channel in the III-N material structure, two terminals, wherein a first terminal is an anode adjacent to the III-N material structure and a second terminal is a cathode in ohmic contact with the electrically conductive channel, and a dielectric layer over at least a portion of the anode. The anode comprises a first metal layer adjacent to the III-N material structure, a second metal layer, and an intermediary electrically conductive structure between the first metal layer and the second metal layer. The intermediary electrically conductive structure reduces a shift in an on-voltage or reduces a shift in reverse bias current of the diode resulting from the inclusion of the dielectric layer. The diode can be a high voltage device and can have low reverse bias currents.

What is claimed is: 
     
         1 . A diode having a threshold voltage, comprising:
 a III-N material structure;   an anode and a cathode on the III-N material structure; and   a dielectric encapsulation layer over at least a portion of the anode, wherein a composition of the anode results in a reverse bias current of the diode per unit width of the anode being less than 1 microamp/mm during reverse bias operation.   
     
     
         2 . The diode of  claim 1 , wherein a voltage across the diode is 1.25V or less for a forward bias current per unit width of the anode of 50 mA/mm. 
     
     
         3 . The diode of  claim 1 , wherein the threshold voltage is 0.7V or less. 
     
     
         4 . The diode of  claim 3 , wherein the reverse bias current of the diode per unit width of the anode is 0.1 microamps/mm or less during reverse bias operation. 
     
     
         5 . The diode of  claim 1 , wherein the threshold voltage is 0.55V or less. 
     
     
         6 . The diode of  claim 1 , wherein a voltage across the diode is 1.1V or less for a forward bias current per unit width of the anode of 50 mA/mm. 
     
     
         7 . The diode of  claim 1 , wherein the anode comprises a first metal layer comprising nickel adjacent to the III-N material structure, a second metal layer comprising gold, and an intermediary electrically conductive structure between the first metal layer and the second metal layer, the intermediary electrically conductive structure comprising a layer of gold adjacent to the first metal layer and a layer of nickel between the layer of gold and the second metal layer. 
     
     
         8 . The diode of  claim 1 , wherein the III-N material structure comprises a first III-N material layer and a second III-N material layer, and a 2DEG channel is induced in a region of the first III-N material layer adjacent the second III-N material layer as a result of a compositional difference between the first III-N material layer and the second III-N material layer. 
     
     
         9 . A diode, comprising:
 a III-N material structure;   an electrically conductive channel in the III-N material structure;   two terminals, wherein a first terminal is an anode adjacent to the III-N material structure, and a second terminal is a cathode in ohmic contact with the electrically conductive channel; and   a dielectric encapsulation layer over at least a portion of the anode, a portion of the cathode, and a surface of the III-N material structure between the anode and the cathode, the dielectric encapsulation layer protecting the diode from contaminants in the surrounding environment, wherein   wherein a composition of the anode causes a shift in an on-voltage of the diode resulting from inclusion of the dielectric encapsulation layer to be less than 0.1V.   
     
     
         10 . The diode of  claim 9 , wherein an increase in reverse bias current of the diode per unit width of the anode resulting from inclusion of the dielectric encapsulation layer is less than 0.9 microamps/mm. 
     
     
         11 . The diode of  claim 9 , wherein the anode comprises a first metal layer comprising nickel adjacent to the III-N material structure, a second metal layer comprising gold, and an intermediary electrically conductive structure between the first metal layer and the second metal layer, the intermediary electrically conductive structure comprising a layer of gold adjacent to the first metal layer and a layer of nickel between the layer of gold and the second metal layer. 
     
     
         12 . The diode of  claim 11 , wherein the III-N material structure comprises a first III-N material layer and a second III-N material layer, and a 2DEG channel is induced in a region of the first III-N material layer adjacent the second III-N material layer as a result of a compositional difference between the first III-N material layer and the second III-N material layer.