Reliability comparison of AlGaN/GaN HEMTs with different carbon doping concentration

Abstract

The reliability of AlGaN/GaN HEMTs adopting Fe and C co-doping, with high and low carbon doping concentration was investigated by means of different stress tests. Firstly, DC and pulsed I-V characterization at room temperature are discussed, then drain step stress tests at different gate voltages are compared, afterwards, the constant stress at different bias points are discussed. Results show that the high C HEMTs showed reduced DIBL, smaller leakage current, as well as decreased electric field, leading to an improved robustness during on-state stress testing, with respect to the reference ones. Failure modes during constant voltage stress consists in a decrease of drain current and transconductance, accelerated by temperature and electric field.

Degradation mechanism of 0.15 μm AlGaN/GaN HEMTs: effects of hot electrons

“…DC characteristics showed that the "Fe Reference" devices have the smallest leakage current; and the "Fe + High C" device has reduced Drain Induced Barrier Lowering (DIBL) effects due to the better charge confinement due to the high carbon doping concentration, as shown in [8]. The EL intensity follows a bell shape versus VGS biasing for all devices, as shown in Fig.…”

“…The demand for industrial-level 0.15 m HEMTs for low-noise and power amplifiers up to and beyond 50 GHz [5] has been enhanced by 5G and radar applications. In order to control short-channel effects, which directly determine leakage current and RF reliability [6], various approaches have been used, including back-barriers [7], C or C+Fe co-doping [8], N-polar GaN/AlGaN channels [9] and so on. Reliability is another key issue that has to be taken into consideration during the improvement of HEMT technologies.…”

“…The degradation mechanisms of the devices could be summarized as trap states generation [10], hot-electron generation [11], gate metal instabilities [12], passivation breakdown [13], inverse piezoelectric effects [14] and so on. For 0.15 m gate length devices, the effects of electric field have proven to be important in reliability [8]. However, there is still not enough study on the combined effects of trapping centres, high electric field and hot electrons.…”

“…This work is a follow up study of [8], comparing 0.15 m gate length GaN HEMTs with different epi design. The devices were fabricated within the same batch, using the same industrial level process, with optimized gate metallization and passivation, on different epi layers.…”

Microwave and Millimeter-Wave GaN HEMTs: Impact of Epitaxial Structure on Short-Channel Effects, Electron Trapping, and Reliability

“…It should be noted, however, that short-term reliability, in particular for what concerns hot-electron effects, also depends on the interplay between charge trapping and electric field distribution. In [80], we compared the on-wafer reliability of 0.15-µm GaN HEMTs for microwave applications adopting Fe and C co-doping, with the same Fe doping profile, but different levels of C doping within the GaN buffer. At increasing C content, short-channel effects were reduced, at the expense of a slightly higher CC, related to the presence of C N acceptors.…”