Initial Study of Ballistic Effects for the Operation of GaAs FET Devices

摘要

Ballistic electron motion at high velocity in the (100) direction in GaAs at both 77 K and room temperature has been determined by current-voltage data on thin layers. Molecular beam epitaxial abrupt layers .4-.5 microns thick with N+ ohmic contacts on both sides, have been tested, and ballistic motion occurs below .5V applied voltage. Layers with a donor density of 1 x 10 to the 15th power/cc, and layers with an acceptor density of 1 x 10 to the 15th power/cc both yield space charge limited current data to agree with the corresponding ballistic transport models developed. Average electron velocity values five times higher than that obtainable in a standard FET are now possible for both 77 K and room temperature in such ballistic electron motion. Although the standard FET geometry, even with short gates, is precluded by thick depletion layers into lightly doped layers, from both the exposed surface and the interface with the semi-insulating substrate, it has been concluded that a ballistic electron transistor with a geometry similar to that of the permeable base transistor is possible for very high speed, high frequency, low noise performance. (Author)