Electrical Characterization and Modeling of GaN HEMTs at Cryogenic Temperatures

In this work, we present a phenomenological cryogenic model for gallium nitride (GaN) high electron mobility transistors (HEMTs) with validity all the way down to a temperature of 10 K, benchmarked with experimental characterization results. The device under test (DUT) for cryogenic characterization is a GaN HEMT with a channel length of 250 nm and a gate width of 40~\mu \text{m} . The characterization results exhibit the negative threshold voltage shifts of −3.437, −3.087, and −2.998 V at the temperatures of 300, 60, and 10 K, respectively. Additionally, kink effects at cryogenic temperatures in output characteristics are observed that behave non-monotonically with gate-to-source bias. The impact of detrapping is modeled to investigate the negative shift in {V}_{\text {TH}} with increasing temperature. To model the kink, the effects of temperature, impact ionization, and field-dependent trapping/detrapping on {V}_{\text {TH}} have been explored and implemented as a submodel in the industry standard Advanced SPICE Model (ASM)-HEMT framework. Here, we aim to overcome the limitations of the prior GaN device models in the quest for enabling GaN-based circuits for cryogenic applications, such as deep space reception, radio astronomy, and quantum computing.