Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

Abstract

In this letter, we have studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with different interface Si donor incorporation which is tuned during the deposition process of LPCVD-SiNx which is adopted as gate dielectric and passivation layer. Current collapse of the MIS-HEMTs without field plate is suppressed more effectively by increasing the SiH2Cl2/NH3 flow ratio and the normalized dynamic on-resistance (RON) is reduced two orders magnitude after off-state VDS stress of 600 V for 10 ms. Through interface characterization, we have found that the interface deep-level traps distribution with high Si donor incorporation by increasing the SiH2Cl2/NH3 flow ratio is lowered. It’s indicated that the Si donors are most likely to fill and screen the deep-level traps at the interface resulting in the suppression of slow trapping process and the virtual gate effect. Although the Si donor incorporation brings about the increase of gate leakage current (IGS), no clear degradation of breakdown voltage can be seen by choosing appropriate SiH2Cl2/NH3 flow ratio.

Comprehensive Comparison of MOCVD- and LPCVD-SiNx Surface Passivation for AlGaN/GaN HEMTs for 5G RF Applications

“…Zhu et al have demonstrated that the surface diffusion of Si is insufficient to compensate for the electron concentration and enhance performance [26]. On the contrary, etching damage accompanied by the diffusion of Si into the semiconductor will generate a leakage current path through the gate, affecting the reverse characteristics of the device [27]. The formation of TiN in high-temperature annealing can promote ohmic metal formation by ensuring direct contact with 2DEG or by forming N vacancies reported by many reports [28][29][30][31].…”

“…According to the results, we suppose that LPCVD can effectively prevent the diffusion of Si. Zhu et al have demonstrated that the surface diffusion of Si is insufficient to compensate for the electron concentration and enhance performance[26].On the contrary, etching damage accompanied by the diffusion of Si into the semiconductor will generate a leakage current path through the gate, affecting the reverse characteristics of the device[27].B. Formation Mechanism of Ohmic Contact…”

The effects of an LPCVD SiN x stack on the threshold voltage and its stability in AlGaN/GaN MIS-HEMTs

“…A trade-off between gate leakage and current collapse as the Si/N ratio varied has been reported by Waller et al [25,26]. Song et al [27] revealed that the hysteresis of V th and the dynamic performance of AlGaN/GaN MIS-HEMTs can be improved by a Si-rich LPCVD-SiN x passivation layer. Huang et al observed an enhanced V th stability and low gate leakage of AlGaN/GaN MIS-HEMT devices with LPCVD-SiN x bilayer stacks using Si-rich SiN x (2 nm) as an interfacial layer capped with a high-resistivity SiN x (15 nm) layer [28].…”

“…Such a large discrepancy in the V th shift suggests the strong effect of SiN stoichiometry on the gate stability of MIS-HEMT devices. A Si-rich SiN x layer tends to result in higher gate stability [27], and the stability can be further enhanced by optimizing the thickness ratio. The sample with a 5 nm/15 nm SN1/SN2 bilayer stack (γ = 0.25) presents the most stable V th (e.g.…”

“…The V th shift phenomenon was improved by using the Si-rich SiN x film as a gate dielectric, which can be qualitatively described by the energetic distribution and density of interface states. It has been reported that the excess Si in Si-rich SiN x can be considered as donors [27,35]. The ionized donor-like SiN x acts as a reservoir of electrons, supplying a large number of electrons to fill the deep-level traps at the SiN x /AlGaN interface and suppressing the charge trapping effect.…”