Experimental Results on Electrical Characteristics of 2DEG Resistors in GaN-on-Si Technology

We report electrical characteristics of two-dimensional electron gas (2DEG) resistors for power integrated circuits (ICs) in GaN-on-Si technology. The 2DEG resistors essentially stem from depletion-mode AlGaN/GaN metal-insulator semiconductor high electron mobility transistors (MIS-HEMTs) with the gate terminal configured open-circuit. From the on-wafer measurements of devices with various layout sizes, the current-voltage (I-V) characteristics display linear behaviour for a voltage drop within ≈ 2 V. Steady DC resistance of the 2DEG resistors ranges from 35 Ωto almost 1 kΩ, with a sheet resistance of about 400 Ω/square. However, when the 2-terminal voltage increases beyond about 3 V, the 2DEG resistors no longer follow Ohm's law: the current starts to level off steadily because of the expected velocity saturation of electrons in GaN. At about 10 V for our fabricated devices, the 2DEG resistance increases non-linearly to about nearly doubled. These characteristics bring implications that 2DEG resistors are useful for small voltage but need proper device modelling for use in especially high-voltage circuits.