AlGaAs/GaAs based HEMTs, inverters and ring oscillators with InGaAs and AlGaAs etch-stop layers

Direct coupled FET logic (DCFL) inverters and 19 stage ring oscillators have been demonstrated with MBE grown AlGaAs/GaAs HEMTs using a dry-etching gate recess technology. Pseudomorphic In_0.3Ga_0.7As and Al_0.3Ga_0.7As were used as etch-stop layers for depleted mode ungated, saturated resistors and enhancement mode FETs, respectively, to achieve excellent uniformities of threshold voltage and saturation current. The maximum extrinsic transconductance of 1.2 mu m gate length devices was 289 mS/mm with 1.35 Omega mm source resistance. The logic swing and noise margins were 0.5 and 0.2 V, respectively. The propagation delay of a 19 stage ring oscillator was 31.5 ps/stage at 300 degrees C.