High-Temperature Operation of AlGaN/GaN HEMTs Direct-Coupled FET Logic (DCFL) Integrated Circuits

This letter presents the high-temperature performance of AlGaN/GaN HEMT direct-coupled FET logic (DCFL) integrated circuits. At 375 degC, enhancement-mode (E-mode) AlGaN/GaN HEMTs which are used as drivers in DCFL circuits exhibit proper E-mode operation with a threshold voltage (V
_TH
) of 0.24 V and a peak current density of 56 mA/mm. The monolithically integrated E/D-mode AlGaN/GaN HEMTs DCFL circuits deliver stable operations at 375 degC: An E/D-HEMT inverter with a drive/load ratio of 10 exhibits 0.1 V for logic-low noise margin (NM
_L
) and 0.3 V for logic-high-noise margin (NM
_H
) at a supply voltage (V
_DD
) of 3.0 V; a 17-stage ring oscillator exhibits a maximum oscillation frequency of 66 MHz, corresponding to a minimum propagation delay ( tau
_pd
) of 446 ps/stage at V
_DD
of 3.0 V