Biosensor based on heterojunction bipolar transistor

Abstract

In one example, a sensor includes a heterojunction bipolar transistor and component sensing surface coupled to the heterojunction bipolar transistor via an extended base component. In another example, a biosensor for detecting a target analyte includes a heterojunction bipolar transistor and a sensing surface. The heterojunction bipolar transistor includes a semiconductor emitter including an emitter electrode for connecting to an emitter voltage, a semiconductor collector including a collector electrode for connecting to a collector voltage, and a semiconductor base positioned between the semiconductor emitter and the semiconductor collector. The sensing surface is coupled to the semiconductor base of the heterojunction bipolar transistor via an extended base component and includes a conducting film and a reference electrode.

What is claimed is: 
     
         1 . A sensor, comprising:
 a heterojunction bipolar transistor; and   a sensing surface coupled to the heterojunction bipolar transistor via an extended base component.   
     
     
         2 . The sensor of  claim 1 , wherein the heterojunction bipolar transistor comprises:
 a semiconductor collector including a collector electrode for connecting to a collector voltage;   a semiconductor base disposed on the semiconductor collector and coupled to the extended base component; and   a semiconductor emitter disposed on the semiconductor base and including an emitter electrode for connecting to an emitter voltage.   
     
     
         3 . The sensor of  claim 2 , wherein the sensing surface comprises:
 a conducting film; and   a reference electrode.   
     
     
         4 . The sensor of  claim 3 , further comprising:
 an aqueous solution containing a target analyte, wherein the conducting film and the reference electrode are immersed in the aqueous solution.   
     
     
         5 . The sensor of  claim 4 , wherein the conducting film comprises titanium nitride. 
     
     
         6 . The sensor of  claim 5 , wherein the target analyte comprises a pH of the aqueous solution. 
     
     
         7 . The sensor of  claim 4 , wherein the conducting film comprises a functionalized conducting metal. 
     
     
         8 . The sensor of  claim 7 , wherein the target analyte comprises a bio-molecule or ion other than a pH of the aqueous solution. 
     
     
         9 . The sensor of  claim 4 , wherein the conducting film comprises silver coated with silver chloride, and the silver chloride is in direct contact with the aqueous solution. 
     
     
         10 . The sensor of  claim 9 , wherein the target analyte comprises a chloride ion. 
     
     
         11 . The sensor of  claim 4 , wherein the conducting film comprised gold. 
     
     
         12 . The sensor of  claim 11 , wherein the target analyte comprises a thiolated bio-molecule. 
     
     
         13 . The sensor of  claim 2 , wherein the semiconductor base comprises P-type doped silicon germanium. 
     
     
         14 . The sensor of  claim 13 , wherein the semiconductor collector comprises N-type doped silicon. 
     
     
         15 . The sensor of  claim 14 , wherein the semiconductor emitter comprises N-type doped polysilicon having a higher dopant concentration than the semiconductor base and the semiconductor collector. 
     
     
         16 . The sensor of  claim 2 , wherein the semiconductor base comprises P-type doped gallium arsenide. 
     
     
         17 . The sensor of  claim 16 , wherein the semiconductor collector comprises N-type doped gallium arsenide. 
     
     
         18 . The sensor of  claim 17 , wherein the semiconductor emitter comprises N-type doped gallium arsenide having a higher dopant concentration than the semiconductor base and the semiconductor collector. 
     
     
         19 . A biosensor for detecting a target analyte, comprising:
 a heterojunction bipolar transistor, the heterojunction bipolar transistor comprising:
 a semiconductor emitter including an emitter electrode for connecting to an emitter voltage; 
 a semiconductor collector including a collector electrode for connecting to a collector voltage; and 
 a semiconductor base positioned between the semiconductor emitter and the semiconductor collector; and 
   component sensing surface coupled to the semiconductor base of the heterojunction bipolar transistor via an extended base component, the sensing surface comprising:
 a conducting film; and 
 a reference electrode. 
   
     
     
         20 . The biosensor of  claim 19 , further comprising:
 an aqueous solution containing the target analyte, wherein the conducting film and the reference electrode of the extended base component are immersed in the aqueous solution.