Temperature-Dependent Study of AlGaAs/InGaAs Integrated Depletion/Enhancement-Mode High Electron Mobility Transistors with Virtual Channel Layers

Recently, we have implemented the direct-coupled FET logic inverters by the AlGaAs/InGaAs co-integrated depletion-mode (D-mode) and enhancement-mode (E-mode) pseudomorphic high electron mobility transistors (PHEMTs) with virtual channel layers in this journal. In this article, the temperature-dependent characteristics of the above integrated PHEMTs will be demonstrated. Due to the two-dimensional electron gas (2DEG) located in the undoped In0.22Ga0.78As layer between two large energy-gap Al0.24Ga0.76As barrier layers, the integrated devices exhibit excellent thermal stability for the good confinement effect in the 2DEG channel. Experimental results exhibit that the maximum transconductance decreases from 162.2 (174.4) to 125.0 (105.8) mS mm-1 for the studied D-mode (E-mode) device as the temperature increases from 300 to 450 K. In addition, the maximum drain current reduces from 366.4 (379.6) at 300 K to 286.4 (254.6) mA mm-1 at 450 K. Significantly, a considerably low temperature coefficient on threshold voltage (∂Vth/∂T) of -0.266 (-0.866) mV K-1 for the D-mode (E-mode) PHEMT is measured, which is superior to the previous reports of the related GaAs-substrate transistors.