Boosted high-temperature electrical characteristics of AlGaN/GaN HEMTs with rationally designed compositionally graded AlGaN back barriers

Wide bandgap GaN-based HEMTs have shown great potential as key components in various power electronic systems but still face challenges in the pursuit of devices with stable operation capability especially in harsh environments. Here, we report a high-performance double heterojunction (DH) based AlGaN/GaN HEMT by incorporating a decreasing-Al-composition (DAC) graded AlGaN back barrier (BB) beneath the GaN channel. Thanks to the improved electron confinement enabled by graded BB, the DHHEMT exhibits significantly improved on-state drain current density and off-state breakdown voltage compared with a single heterojunction (SH) based HEMT. More intriguingly, with an additional SiN x passivation layer, the surface states of the DH-HEMTs can be effectively suppressed, leading to an almost constant off-state leakage current and negligible gate contact degradation across the temperature range from 25° C to 150° C. These results highlight the superiority and reliability of the proposed graded AlGaN BB to boost device characteristics for applications under high temperatures and harsh conditions.