Enhancement of Breakdown Voltage in AlGaN/GaN HEMTs: Field Plate Plus High-<inline-formula> <tex-math notation="LaTeX">${k}$ </tex-math> </inline-formula> Passivation Layer and High Acceptor Density in Buffer Layer

Abstract

We make a 2-D analysis of breakdown characteristics of field-plate AlGaN/GaN HEMTs with a high-k passivation layer, and the results are compared with those having a normal SiN passivation layer. As a result, it is found that the breakdown voltage is enhanced particularly in the cases with relatively short field plates because the reduction in the electric field at the drain edge of gate effectively improves the breakdown voltage in the case with the high-k passivation layer. In the case with the moderate-length field plate, the enhancement of breakdown voltage due to the high-k passivation layer occurs because the electric field profiles between the field-plate edge and the drain become more uniform. It is also studied how the breakdown voltage depends on a deep-acceptor density in the Fe-doped semiinsulating buffer layer when a high-k passivation layer is used. It is shown that the breakdown voltage increases with increasing the relative permittivity of the passivation layer ε r and with increasing the deep-acceptor density N DA . When ε r = 60 and N DA = 2-3 × 10 17 cm −3 at the gate length of 0.3 μm, the breakdown voltage becomes about 500 V at a gate-to-drain distance of 1.5 μm, which corresponds to an average electric field of about 3.3 MV/cm between the gate and the drain. Index Terms-2-D analysis, breakdown characteristics, buffer layer, GaN HEMT, high-k passivation layer. I. INTRODUCTION N OWADAYS, AlGaN/GaN HEMTs are attractive for applications to high-power microwave devices and highpower switching devices [1], [2]. It is well known that introducing a field plate enhances the power performance of AlGaN/GaN HEMTs as well as GaAs FETs [3]-[5]. This occurs because by introducing a field plate, the current collapse is reduced [6], [7], and the breakdown voltage increases [8]-[10]. The increase in breakdown voltage occurs because the electric field at the drain edge of gate is reduced by introducing a field plate.

High-Voltage Normally-off Recessed Tri-Gate GaN Power MOSFETs With Low on-Resistance

“…In addition, despite the lack of passivation in both devices, this additional FP also improved the dynamic RON of the recessed tri-gate devices by better distributing the electric field under the gate, as supported by [30], [31] (inset of Fig.4 (b)). The measured floating breakdown voltage could be affected by virtual gating, which can be resolved by a proper passivation process without sacrificing the breakdown voltage [32]- [34].…”

Simulation of AlGaN/GaN HEMTs’ Breakdown Voltage Enhancement Using Gate Field-Plate, Source Field-Plate and Drain Field Plate

“…The permittivity of SiO 2 was set to 5, corresponding to the value of the experimental measurement. Likewise, Si 3 N 4 [25] and Al 2 O 3 [26] could also be selected as passivation, and the kind of insulator would not change the trend of V BD versus FPs [19]. The thickness of insulator layer t 1 and t 2 ; length of FPs L FP-G , L FP-S and L FP-D ; and the thickness of FPs t FP-G and t FP-S are variable in the following Section.…”

“…The leakage current [27], especially from the buffer layer, may result in electron injection from the channel into the buffer layer and a large drain current [28]. Setting traps in the GaN buffer is a usual way to decrease the leakage current at pinch-off state [19,29,30], but it may cause a no-convergence problem. Moreover, we aimed to present the relevance between electric field distributions and FPs clearly and exclude the punch-through from the buffer layer.…”

“…An extremely high V BD of 8300 V was achieved by using the thick poly-AlN passivation on HEMTs with both FP-G and FP-S [18]. Toshiki Kabemura et al made a 2-D analysis of breakdown characteristics of FP HEMTs with a high-k passivation layer, confirming that the V BD would increase with relative permittivity increasing [19]. For investigating the impact of FP-G and FP-S on the capacitances, Aamir et al modeled the bias dependence of terminal capacitances, and the proposed model is in excellent agreement with measured data [20].…”

Low-temperature and ammonia-free epitaxy of GaN/AlGaN/GaN heterostructure

“…III-nitrides have been intensively studied in view of their interesting applications as electronics and optoelectronics components, including light-emitting diodes (LEDs), laser-diodes (LDs), 1,2 and highpower/high frequency high electron mobility transistors (HEMTs). 3 GaN-based devices, primarily fabricated on foreign substrates because of the lack of high quality and large area GaN substrates, exploit the semiconductor technology reference deposition techniques of molecular beam epitaxy (MBE), and metal organic chemical vapour deposition (MOCVD). These techniques are characterised by significant production costs, as they require, respectively, either ultra-high vacuum conditions, or energy consuming procedures involving high growth temperatures (in the 1000 °C range), 4 and large flows of critical handling gases like ammonia (NH3).…”