High responsivity device for thermal sensing in a terahertz radiation detector

Abstract

There is provided a novel and useful a high responsivity device for thermal sensing in a Terahertz (THz) radiation detector. A load impedance connected to an antenna heats up due to the incident THz radiation received by the antenna. The heat generated by the load impedance is sensed by a thermal sensor such as a transistor. To increase the responsivity of the sense device without increasing the thermal mass, the device is located underneath a straight portion of an antenna arm. The transistor runs substantially the entire length of the antenna arm alleviating the problem caused by placing large devices on the side of the antenna and the resulting large additional thermal mass that must be heated. This boosts the responsivity of the pixel while retaining an acceptable level of noise and demanding a dramatically smaller increase in the thermal time constant.

What is claimed is: 
     
         1 . A thermal sensor for use in a terahertz (THz) radiation detector having one or more antenna arms, comprising:
 an electrical device adapted to respond to changes in temperature; and   wherein said device is located beneath at least one of said antenna arms of said detector.   
     
     
         2 . The sensor according to  claim 1 , wherein said electrical device comprises a transistor. 
     
     
         3 . The sensor according to  claim 1 , wherein said electrical device comprises a diode. 
     
     
         4 . The sensor according to  claim 1 , wherein said electrical device comprises a resistor. 
     
     
         5 . The sensor according to  claim 1 , wherein said electrical device comprises a device whose current (I)-voltage (V) characteristic is temperature dependent. 
     
     
         6 . The sensor according to  claim 1 , wherein said electrical device is substantially covered by an antenna arm. 
     
     
         7 . The sensor according to  claim 1 , wherein said electrical device is under a straight portion of an antenna arm. 
     
     
         8 . The sensor according to  claim 1 , wherein the size of said electrical device is the longest able to fit under an antenna arm. 
     
     
         9 . The sensor according to  claim 1 , wherein said electrical device comprises a transistor whose width substantially fits under an antenna arm. 
     
     
         10 . The sensor according to  claim 1 , wherein said electrical device comprises a transistor whose length substantially fits under an antenna arm. 
     
     
         11 . The sensor according to  claim 1 , further comprising one or more additional electrical devices, each placed under a different antenna arm. 
     
     
         12 . The sensor according to  claim 11 , wherein said plurality of electrical devices are connected in parallel so as to increase effective device size. 
     
     
         13 . A thermal sensor for use in a terahertz (THz) radiation detector having one or more antenna arms, comprising:
 a transistor responsive to changes in temperature; and   wherein said device is located substantially completely beneath an antenna arm of said detector.   
     
     
         14 . The sensor according to  claim 13 , wherein said electrical device comprises a transistor whose width substantially fits under an antenna arm. 
     
     
         15 . The sensor according to  claim 13 , further comprising one or more additional transistors, each placed under a different antenna arm. 
     
     
         16 . The sensor according to  claim 15 , wherein said plurality of transistors are connected in series or parallel so as to increase their effective size. 
     
     
         17 . A method of fabricating a thermal sensor for use in a terahertz (THz) radiation detector having one or more antenna arms, comprising:
 providing a semiconductor substrate;   fabricating an electrical device responsive to changes in temperature on said substrate along a path of an antenna arm; and   fabricating the conductive portion of said antenna arm directly over said electrical device such that the width of said electrical device is the longest that can fit under said antenna.   
     
     
         18 . The method according to  claim 17 , wherein said electrical device comprises a transistor. 
     
     
         19 . The method according to  claim 17 , wherein said electrical device comprises a diode. 
     
     
         20 . The method sensor according to  claim 17 , wherein said electrical device comprises a resistor. 
     
     
         21 . The method according to  claim 17 , wherein said electrical device comprises a device whose current (I)-voltage (V) characteristic is temperature dependent. 
     
     
         22 . The method according to  claim 17 , further comprising one or more additional electrical devices, each placed under a different antenna arm. 
     
     
         23 . The method according to  claim 22 , wherein said plurality of electrical devices are connected in parallel so as to increase its effective size. 
     
     
         24 . A detector for detecting terahertz (THz) radiation, comprising:
 an antenna having one or more elements supported by a holding arm;   a load impedance directly coupled to said antenna and operative to convert said received terahertz radiation to thermal energy; and   a thermal sensor operative to generate an electrical signal in accordance with the heat generated by said load impedance, wherein said thermal sensor located underneath at least a portion of said antenna.