Thermal effects in n-channel enhancement MOSFET's operated at cryogenic temperatures

Thermal effects in n-channel enhancement-mode MOSFET's operated at cryogenic temperatures are discussed. Device heating is identified as the cause of drain current transients and the origin of this phenomenon is considered. Experimental results are presented in which thermal effects are studied as functions of temperature for various gate and drain biases. Drain current is found to be a monitor of device temperature, From an understanding of the thermal behavior of devices, the channel electron mobility can be examined as a function of temperature and gate bias. The observed thermal effects are explained in terms of material and device properties. The implications for future low-temperature CMOS VLSI development are discussed.