Electric-stress reliability and current collapse of different thickness SiNx passivated AlGaN/GaN high electron mobility transistors

This paper investigates the impact of electrical degradation and current collapse on different thickness SiNx passivated AlGaN/GaN high electron mobility transistors.It finds that higher thickness SiNx passivation can significantly improve the high-electric-field reliability of a device.The degradation mechanism of the SiNx passivation layer under ON-state stress has also been discussed in detail.Under the ON-state stress,the strong electric-field led to degradation of SiNx passivation located in the gate-drain region.As the thickness of SiNx passivation increases,the density of the surface state will be increased to some extent.Meanwhile,it is found that the high NH 3 flow in the plasma enhanced chemical vapour deposition process could reduce the surface state and suppress the current collapse.     

Various Recipes of SiNx Passivated AlGaN/GaN High Electron Mobility Transistors in Correlation with Current Slump

The current slump of different recipes of SiN~ passivated AIGaN/GaN high electron mobility transistors （HEMTs） is investigated. The dc and pulsed current-voltage curves of AIGaN/GaN HEMTs using different recipes are analyzed. It is found that passivation leakage has a strong relationship with NH3 flow in the plasma-enhanced chemical vapor phase deposition process, which has impacted on the current collapse of SiNs passivated devices. We analyze the pulsed IDS -- VDS characteristics of different recipes of SiNx passivation devices for different combinations of gate and drain quiescent biases （VGso, VDSO） of （0, 0）, （-6, 0）, （-6, 15） and （0, 15）V. The possible mechanisms are the traps in SiNxpassivation capturing the electrons and the surface states at the SiNx/AIGaN interface, which can affect the channel of two-dimensional electron gas and cause the current collapse.     

增强型AlGaN/GaN高电子迁移率晶体管高温退火研究

深入研究了两种增强型AlGaN/GaN高电子迁移率晶体管(HEMT)高温退火前后的直流特性变化.槽栅增强型AlGaN/GaN HEMT在500 ℃ N₂中退火5 min后,阈值电压由0.12 V正向移动到0.57 V,器件Schottky反向栅漏电流减小一个数量级.F注入增强型AlGaN/GaN HEMT在 400 ℃ N₂中退火2 min后,器件阈值电压由0.23 V负向移动到-0.69 V,栅泄漏电流明显增大.槽栅增强型器件退火过程中Schottky有效势垒     

中子辐照对AlGaN/GaN高电子迁移率晶体管器件电特性的影响

本文采用能量为1 MeV的中子对SiN钝化的AlGaN/GaN HEMT(高电子迁移率晶体管)器件进行了最高注量为1015cm-2的辐照.实验发现:当注量小于1014cm-2时,器件特性退化很小,其中栅电流有轻微变化(正向栅电流IF增加,反向栅电流IR减小),随着中子注量上升,IR迅速降低.而当注量达到1015cm-2时,在膝点电压附近,器件跨导有所下降.此外,中子辐照后,器件欧姆接触的方块电阻退化很小,而肖特基特性退化却相对明显.通过分析发现辐照在SiN钝化层中引入的感生缺陷引起了膝点电压附近漏电流和反向栅泄漏电流的减小.以上结果也表明,SiN钝化可以有效地抑制中子辐照感生表面态电荷,从而屏蔽了绝大部分的中子辐照影响.这也证明SiN钝化的AlGaN/GaN HEMT器件很适合在太空等需要抗位移损伤的环境中应用.     

Characterization of Al2O3 /GaN/AlGaN/GaN metalinsulator-semiconductor high electron mobility transistors with different gate recess depths

In this paper,in order to solve the interface-trap issue and enhance the transconductance induced by high-k dielectric in metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs),we demonstrate better performances of recessed-gate Al 2 O 3 MIS-HEMTs which are fabricated by Fluorine-based Si 3 N 4 etching and chlorinebased AlGaN etching with three etching times (15 s,17 s and 19 s).The gate leakage current of MIS-HEMT is about three orders of magnitude lower than that of AlGaN/GaN HEMT.Through the recessed-gate etching,the transconductance increases effectively.When the recessed-gate depth is 1.02 nm,the best interface performance with τ it =(0.20-1.59) μs and D it =(0.55-1.08)×10 12 cm 2 ·eV 1 can be obtained.After chlorine-based etching,the interface trap density reduces considerably without generating any new type of trap.The accumulated chlorine ions and the N vacancies in the AlGaN surface caused by the plasma etching can degrade the breakdown and the high frequency performances of devices.By comparing the characteristics of recessed-gate MIS-HEMTs with different etching times,it is found that a low power chlorine-based plasma etching for a short time (15 s in this paper) can enhance the performances of MIS-HEMTs effectively.     

Enhancement-mode AlGaN/GaN high electronic mobility transistors with thin barrier

An enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMTs) was fabricated with 15-nm AlGaN barrier layer. E-mode operation was achieved by using fluorine plasma treatment and post-gate rapid thermal annealing. The thin barrier depletion-HEMTs with a threshold voltage typically around --1.7 V, which is higher than that of the 22-nm barrier depletion-mode HEMTs (--3.5 V). Therefore, the thin barrier is emerging as an excellent candidate to realize the enhancement-mode operation. With 0.6-μ m gate length, the devices treated by fluorine plasma for 150-W RF power at 150 s exhibited a threshold voltage of 1.3 V. The maximum drain current and maximum transconductance are 300 mA/mm, and 177 mS/mm, respectively. Compared with the 22-nm barrier E-mode devices, V_T of the thin barrier HEMTs is much more stable under the gate step-stress.     

Investigation of AlGaN/GaN fluorine plasma treatment enhancement-mode high electronic mobility transistors by frequency-dependent capacitance and conductance analysis

This paper reports fluorine plasma treatment enhancement-mode HEMTs (high electronic mobility transistors) EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology. It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance--voltage measurement. Using capacitance--frequency measurement, it finds one type of trap in conventional DHEMTs with τ_T=(0.5-6) ms and D_T= (1 - 5) × 10¹³ cm^-2·eV^-1. Two types of trap are found in fluorine plasma treatment EHEMTs, fast with τ_T(f)=(0.2-2) μs and slow with τ_T(s)=(0.5-6) ms. The density of trap states evaluated on the EHEMTs is D_T(f)=(1 - 3) × 10¹² cm^-2·eV^-1 and D_T(s)=(2 - 6) × 10¹² cm^-2·eV^-1 for the fast and slow traps, respectively. The result shows that the fluorine plasma treatment reduces the slow trap density by about one order, but introduces a new type of fast trap. The slow trap is suggested to be a surface trap, related to the gate leakage current.     

AlGaN/GaN槽栅HEMT模拟与实验研究

分析了栅槽深度对AlGaN/GaN HEMT特性的影响,并对不同栅槽深度的器件特性进行了模拟,得到了器件饱和电流、最大跨导和阈值电压随栅槽深度的变化规律.当槽栅深度增大,器件饱和电流逐渐下降,而最大跨导逐渐增大,阈值电压向X轴正方向移动.研制出不同栅槽深度的蓝宝石衬底AlGaN/GaN HEMT,用实验数据验证了得到的不同栅槽深度器件特性变化规律.从刻蚀损伤和刻蚀引入界面态的角度分析了模拟与实验规律产生差别的原因. 关键词： 高电子迁移率晶体管 AlGaN/GaN 槽栅器件     

AlGaN/GaN MIS-HEMT using NbAlO dielectric layer grown by atomic layer deposition

We present an AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) with an NbAlO high-k dielectric deposited by atomic layer deposition (ALD).Surface morphology of samples are observed by atomic force microscopy (AFM),indicating that the ALD NbAlO has an excellent-property surface.Moreover,the sharp transition from depletion to accumulation in capacitance-voltage (C-V)curse of MIS-HEMT demonstrates the high quality bulk and interface properties of NbAlO on AlGaN.The fabricated MIS-HEMT with a gate length of 0.5 μm exhibits a maximum drain current of 960 mA/mm,and the reverse gate leakage current is almost 3 orders of magnitude lower than that of reference HEMT.Based on the improved direct-current operation,the NbAlO can be considered to be a potential gate oxide comparable to other dielectric insulators.