In-situ mobility profiling of GaAs MESFET's using the hall current technique

A novel experimental technique to perform in-situ Hall effect mobility profiling of short-channel devices is described in this paper. This is based on the measurement of the Hall current in the conduction channel of a transistor with a split source or drain contact. The mobility is then determined by a simple expression relating the Hall current, the physical dimensions of the channel, the total current injected in the device, and the magnetic induction. No special structure is required and the measurements can be performed on the usual MESFET or MODFET geometries. The same technique can also be used with devices fabricated on lower mobility materials such as silicon where the geometrical magnetoresistance measurements are not practical. Using the new technique, we have obtained spatial Hall mobility profiles in commercially available GaAs MESFET's. Our experimental results are in good agreement with data obtained by other researchers using magnetoresistance measurements. Finally, some theoretical and practical problems associated with our technique are discussed.