The Impact of Bias Conditions on Self-Heating in AlGaN/GaN HEMTs

The thermal response of AlGaN/GaN high electron mobility transistors directly correlates with the overall performance and reliability of these devices. In general, a hot spot develops near the drain end of the gate electrode during power dissipation. The device channel temperature was examined via micro-Raman spectroscopy under various bias conditions where power dissipation levels were identical. Under these bias conditions, difference in internal states (sheet carrier density and electric held distribution) within the device alters the heat generation profile across the channel. High V_ds conditions lead to significantly higher channel temperature compared to that for low V_ds conditions although the power dissipation is kept constant. Experimental results show ~13°C deviation between V_ds = 45 V and V_ds = 7 V cases when the power dissipation is 4.5 W/mm. This suggests that bias conditions may have a relatively signihcant impact on device reliability and that this effect must be considered when building thermal models of devices under operation or undergoing accelerated life testing.