On-chip Heating Effects in Electronic Measurements at Cryogenic Temperatures

Heating is a major concern for electrical measurements at cryogenic temperatures. In this study, the statics and dynamics of heating effects induced on a Si/SiO2 chip by the application of DC and AC power to an on-chip heating element are measured using on-chip cryogenic thermometers. It is found that large on chip tempera-tures, -100 mK above cryostat temperature, and large on-chip thermal gradients, 100s of mK over -10 mu m distance, are generated at relatively small (-0.1 mu W) input powers. As expected, the heating effects are larger at lower cryostat temperatures. With applied AC voltages, it is found that the average temperatures generated are similar in magnitude to the DC voltages, but the temperature gradients are smaller. The average temperatures reached on the surface of the chip increase with increasing frequency. At 5 Hz frequency, the thermal dynamics are too slow to allow temperature oscillations following the input power, instead resulting in a steady state temperature increase.