Use this search method to see the network around the inventors of all patents that the US Patent and Trademark office classified as fitting within a particular technology sub-class.
For example, if you want to see the world of inventors around doped semiconductors, you might enter Main Class 438 (''), Sub Class 151 ('').
While sub-classes are narrow, this search starts from inventors of ALL patents in this sub-class. This comprehensive view means that it gets big really fast, so 1-2 degrees of co-invention at most are recommended, and a short time span.
You can find this information by going to Google Patents, finding the patent you wish to know its classifications, and looking in the Classifications section. That section is highlighted in the following example image: classifications_guide.png