Voltage distributions in X-band n/+/-n-n/+/ Gunn devices using a SEM

Results obtained by using the electron beam probe of a scanning electron microscope (SEM) in the voltage contrast mode, as a voltage measuring probe to ascertain voltage distributions in mesa structure Gunn devices, are presented. The work is an extension of the Gopinath-Hill technique (1974), and results obtained with GaAs and InP mesa geometry n(+)-n-n(+) sandwich structure devices with active layers of about 8 microns, and operated as oscillators or amplifiers, are reported. Measurement errors, typical results of voltage distributions obtained under both static and dynamic conditions, and comparison of the result with computer simulations in the literature, are presented. The voltage profile along the Gunn device active gap, high-field behavior, and stable-field profiles are obtained.