High-temperature characteristics of 2-D MESFETs

Experimental data of 2-D MESFETs, which utilize sidewall Schottky contacts to degenerate two-dimensional electron gas, indicate a much weaker temperature dependence of the drain current compared to conventional MESFETs in the temperature range from 25-150/spl deg/C. Measured drain current characteristics show that the 2-D MESFET structure exhibits negligible threshold voltage shift with temperature in this temperature range. The negligible threshold voltage shift can be explained in terms of a nearly temperature independent built-in voltage related to the degeneracy of the two-dimensional electron gas. Furthermore, the low-field mobility extracted from the measured transconductance exhibits a smaller degradation with increasing temperature compared to conventional MESFETs. For our devices, the mobility drops by approximately 25% over the temperature range 25-125/spl deg/C, compared to 40-50% for conventional MESFETs. The smaller temperature variations of the low-field mobility are linked to a more effective screening of impurity scattering by the two-dimensional electron gas.