First Measurements of a Microwave Frequency Comb with a Semiconductor Sample in a Scanning Tunneling Microscope
The first two harmonics of a microwave frequency comb (MFC) were measured at a probe which must be within 1 mm of the tunneling junction at the surface of a semiconductor as the sample electrode in a scanning tunneling microscope. The MFC was generated using a passively mode locked Ti:Sapphire laser with GaN, but lasers with lower photon energy would be required with silicon. The attenuation of the MFC is primarily caused by the spreading resistance in a sub nm spot at the tunneling junction. Thus, the measured attenuation could be used to determine the carrier density at this spot as an extension of scanning spreading resistance microscopy (SSRM) We anticipate that this effect will enable new nondestructive methods for sub nm carrier profiling of semiconductors.
2016 IEEE Workshop on Microelectronics and Electron Devices (WMED)