High sensitivity semiconductor strain gauge

Abstract

A method and device for measuring strain in which the resistance of a layer of piezoelectric semiconductor material is measured across a dimension along which the resistance is strain sensitive by a gauge factor of at least 100.

I claim: 
     
       1. A semiconductor strain transducer assembly, comprising: a layer of piezoelectric semiconductor material of single conductivity type having a .Iadd.hexagonal wurtzite crystal structure and having a .Iaddend.strain sensitive resistivity along .[.a predetermined direction, said layer being chosen from the group consisting essentially of cadmium sulfide, zinc sulfide, cadmium selenide, zinc selenide, cadmium oxide, zinc oxide, cadmium telluride, zinc telluride, aluminum nitride, gallium nitride, indium nitride, thallium nitride, aluminum phosphide, gallium phosphide, indium phosphide, thallium phosphide, aluminum arsenide, gallium arsenide, indium arsenide, thallium arsenide, aluminum antimonide, gallium antimonide, indium antimonide, thallium antimonide, and alloys thereof so that said resistivity.]. .Iadd.its C axis which .Iaddend.is strain sensitive by a gauge factor of at least 100;   electrical contacts defining a current path parallel to said .[.predetermined direction.]. .Iadd.C axis; .Iaddend.   means for applying a voltage across said electrical contacts;   means for measuring the resistance between said electrical contacts while said voltage is applied;   means for securing said layer to a member to which strain forces under investigation are to be applied; and   means for applying said strain forces under investigation to said member.   
     
     
       2. The invention according to claim 1 in which said semiconductor material is cadmium sulfide. 
     
     
       3. The invention according to claim 1 in which said electrical contacts comprise a first conductive electrode on a surface of said layer for providing a first terminal connection and a second conductive electrode disposed on a second surface of said layer, opposite said first surface, for providing a second terminal connection. 
     
     
       4. The invention according to claim 3 in which said second surface is diffused with an impurity. 
     
     
       5. The invention according to claim 4 wherein said impurity comprises cupric chloride. 
     
     
       6. The invention according to claim 5 wherein said semiconductor material is cadmium sulfide. 
     
     
       7. The invention according to claim 3 wherein said first conductive electrode comprises gold. 
     
     
       8. The invention according to claim 3 wherein said second conductive electrode comprises a first metal having a low work function in contact with said second surface of semiconductor material and a second, different, metal thereon. .Iadd. 9. The invention according to claim 1 in which said layer of semiconductor material is cadmium sulfide, zinc sulfide, cadmium selenide, zince oxide, gallium nitride, indium nitride, or aluminum nitride. .Iaddend..Iadd. 10. The invention according to claim 1 in which said layer of semiconductor material is 2-25 microns thick. .Iaddend..Iadd. 11. The invention according to claim 1 in which said layer of semiconductor material includes electronically active components diffused into a surface portion thereof to a depth of 10-100 A along said C axis. .Iaddend.