Magnetically Tuned Varistor and Its Embedded Transistors

This paper describes the properties and potential applications of a hybrid device consisting of a varistor diode and its embedded transistor whose origin lies in a magnetically tuned varistor diode. It is shown how the output current (or voltage) of a varistor based on a magnetic oxide semiconductor can be manipulated by the application of a magnetic field to produce an embedded device with characteristics similar to that of a conventional transistor. Following the tradition of microelectronics, we name it the HFET transistor where H stands for a magnetic field. Two types of embedded HFET devices are described here; one with the current–voltage (I–V) characteristics and the other with voltage–current (V–I) characteristics. Both I–V and V–I devices exhibit high degree of nonlinearly but only in the V–I mode of the HFET device well-developed saturation regions of output signals are found. The room temperature HFET in its V–I mode appears to be also a good electronic switch with well-defined “off” and “on” states. Saturated regions of output signals and electronic switching are the signature property of these HFET transistors along with the capacity of providing a good level of signal amplification. When cooled to 100 K the HFET V-I device appears to lose partially the electronic switching property but gain in signal amplifying potential. The HFET device in I–V mode does not display the defining properties of electronic switching but can amplify signals by almost 400%.