GaN HEMT Power Devices Research Articles

Degradation of electrical performance and radiation damage mechanism of cascode GaN HEMT with 80 MeV proton

In this paper, proton irradiations on Cascode GaN HEMT power device with an energy of 80 MeV and fluences of 2 × 1011 p/cm2 and 6 × 1011 p/cm2 have been carried out, where the threshold voltages drifted negatively by 20.55% and 28.17%, respectively. After two months of room temperature annealing, the threshold voltages recovered 0.22 V and 0.27 V, respectively. The ionizing deposition energy (IEL) was simulated by using Monte Carlo software and TCAD, it the results showed that the value of IEL in Si MOSFET is 5 ∼ 6 orders higher than that in GaN HEMT, while the value of the non-ionizing energy loss (NIEL) is one order higher than that in GaN HEMT. It means that the proton irradiation on the Cascode depleted GaN HEMT is more prone to produce displacement damage. As a large number of electrons and holes pairs were existed on the incident path of Si MOSFET under the proton irradiation, the produced electron will be captured by the gate oxide traps at the SiO2/Si interface, and the holes be captured by the defects generated in displacement damage, resulting in the accumulation of oxide trapped charges. Then, the electrical performance of Si MOSFET degrades seriously, thereby affecting the performance of the entire device. The studies will be helpful for the radiation hardening of Cascode GaN HEMT.

Junction temperature prediction method of GaN HEMT power devices based on accurate on-voltage testing

Compared with Si devices, GaN HEMT has lower on-resistance, lower junction capacitance, higher switching frequency, higher switching speed and higher junction temperature capability. It is widely used in automotive, aerospace and other fields. Severe environments may cause the junction temperature of GaN-HEMT to be too high, and excessive temperature is the main reason for power device failure. In order to ensure stable operation of GaN devices under harsh conditions, it is important to extract junction temperature information of semiconductor devices simply and effectively. However, most of the existing junction temperature prediction methods are not applicable to GaN HEMT devices due to its high switching speed and high requirement of prediction accuracy. Thus, we proposed a new method based on an accurate on-voltage clamp circuit to predict the junction temperature of GaN HEMT devices. The interrelation between the on-resistance and the junction temperature is analyzed, and the temperature coefficient is calibrated to obtain the corresponding relationship between the characterization quantity and the junction temperature. The on-resistance testing circuit suitable for GaN device is given and analyzed in detail. Finally, the conduction resistance testing circuit is used to predict the junction temperature of GaN devices, achieving extremely high accuracy. Experiments have verified under 100 ℃, the predicted junction temperature and the actual junction temperature have achieved more than 90% coincidence.

Over-voltage and cross-conduction hard switching stress on schottky gate-type p-GaN HEMT in half-bridge operation. Experimental and physical approaches

The GaN HEMT power device emerges as a promising wide-bandgap component for obtaining ultra-compact and very high efficiency power converters. Nevertheless, its long-time switching operation capability in high overload regimes near or just above its maximum ratings remains unknown. The physical degradation mechanisms specific to GaN HEMT as well as the associated electrical signatures must now be established and better understood. In this article a stress protocol is proposed combining or not functional drain-source over-voltage switching and transient low dead-time cross-conduction stresses. A no-loaded Half Bridge (HB) is used. All stress parameters studied have been associated to electric changes such as drain-source, gate-source leakage currents, and threshold voltage drifts of intrinsic values and even some physical degradation by LIT compound analysis. After analysis, it appears that both the electric field and the current are very stressful for the devices and lead to current leakage caused by physical degradation. The aging observed might be generated from the injection of hot electrons and located depending upon the drain voltage value which influences the depletion region and thus the electric field peak.

Comprehensive investigation on different ions of geostationary orbit induced single event burnout in GaN HEMT power devices

In this paper, the single event burnout (SEB) in p-GaN gate HEMT power devices induced by various ions of the geostationary orbit (GEO) has been studied via simulation. The linear energy transfer (LET) values and incident depths of different ions are determined by SRIM (stopping and range of ions in matter) software, and the electrical properties of the devices under irradiation are studied by Silvaco. It is found that the SEB is caused by the corresponding high electric field and the current crowding. The sensitive injection position is in the middle of the drift region. The threshold voltage of SEB (VSEB) decreases under heavier ion irradiation. The safe operating voltage area of the device under different ions' irradiation is given. Meanwhile, the SEB failure probability of each ion in low years of GEO is evaluated, and the device is most likely to be vulnerable to H ions. Finally, the hardened structure against SEB of GaN HEMT power devices is proposed.

GaN MIS-HEMT with Low Dynamic ON-Resistance Using SiON Passivation

GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have demonstrated outstanding high-power and high-frequency performance [1]. However, the large amount of surface states at the GaN surface, which cannot be totally removed, leads to the current slump when the GaN HEMTs operate under the high drain bias [2]. Therefore, the surface passivation becomes a very important issue for GaN HEMT power device. To eliminate the surface states at the GaN surface, many groups have performed different passivation methods using different deposition techniques, materials, and surface treatments. However, only a few papers reported the correlation between device performance and the surface potential due to the passivation with different charge density. The effect of charge passivation was demonstrated in this study. It was reported that SiON has high density of positive fixed charge (Q f) in the bulk due to the incorporation of nitrogen into oxide which generates high density of positively charged K+center [3]. The positive fixed charges at the SiON/GaN interface can reduce the negative GaN surface potential, expanding the 2DEG quantum well below the Fermi level and stabilizing the 2DEG carrier density when the device operates under high electric field. Thus, SiON has many desired properties as the passivation layer and gate insulator for GaN MIS-HEMT. The AlGaN/GaN HEMT heterostructure was grown by metal-organic chemical vapor deposition (MOCVD) on silicon substrate. The 12-nm SiON and SiN films were adopted as the passivation and gate insulator layers for device performance comparison. These films were prepared by plasma-enhanced chemical vapor deposition system at 300°C. The device fabrication features Ti/Al/Ni/Au ohmic contact metal and Ni/Au gate metal. The schematic cross section of the AlGaN/GaN HEMT with passivation layer and gate insulator is shown in Fig. 1. The gate-to-drain spacing L GD, gate-to-source spacing L GS, and gate length L G were 10-μm, 3-μm, and 2-μm, respectively. The large negative ΔV th observed for the sample with SiON passivation indicates the existence of high density of positive fixed charge at SiON/AlGaN interface. The density of positive fixed charges were ~2.7 × 1013 and ~1.5 × 1013 e/cm-2 for SiON and SiN, respectively. The basic DC I‒V characteristics are shown in Fig. 2. For the sample with SiON passivation, a higher I DS,max of >1 A/mm, and a lower subthreshold slope (SS) of 68 mV/dec were obtained. In contrast, the sample with SiN passivation exhibits a I DS,max of ~896 mA/mm, and a SSof 73 mV/dec. It indicates that the positive fixed charges at the SiON/AlGaN interface reduce the negative GaN surface potential and expand the quantum well below the Fermi level, resulting in the increase of the 2DEG carrier density. The dynamic ON-resistance has been commonly used to examine the trapping effects attributed to the surface and interface states in the GaN device structure [4]. As shown in Fig. 3, the dynamic ON-resistance were extracted by varying OFF-state drain quiescent voltage (V DSQ) of 0 ~ 100 V and ON-state with V GS = 0 V, V DS = 1 V. The ON-state pulse width was 500 μs with a duty cycle of 10%. For the V DSQstress at 100 V, the dynamic ON-resistance increases slightly to 1.03 times for the sample with SiON passivation. In contrast, the dynamic ON-resistance increases 1.17 times for the sample with SiN passivation. The results reveal that SiON passivation with high density of positive fixed charge for GaN MIS-HEMT is preferable for power device applications. With high-density positive charge passivation using SiON, the GaN MIS-HEMT demonstrates the improvements in I‒Vcharacteristics and dynamic ON-resistance. Overall, the results demonstrate that the high density of positive charge in the film is a promising passivation and gate insulator for GaN power devices. Fig. 1. Schematic cross section of the GaN MIS-HEMT Fig. 2. (a) I DS–V DScharacteristics and (b) transfer characteristics for GaN MIS-HEMTs with different passivation and gate insulator layers. Fig. 3. Switching performance extracted from various OFF-state quiescent bias of 0 ~ 100 V. [1] W. Saito, Y. Takada, M. Kuraguchi, K. Tsuda, I. Omura, T. Ogura and H. Ohashi, Electron Devices, IEEE Transactions on 50 (12), 2528-2531 (2003). [2] R. Vetury, N. Q. Zhang, S. Keller and U. K. Mishra, Electron Devices, IEEE Transactions on 48 (3), 560-566 (2001). [3] Z. Zhuo, Y. Sannomiya, Y. Kanetani, T. Yamada, H. Ohmi, H. Kakiuchi and K. Yasutake, Nanoscale research letters 8 (1), 1-6 (2013). [4] D. Jin and J. del Alamo, Electron Devices, IEEE Transactions on 60 (10), 3190-3196 (2013). Figure 1

An X‐band RLC matched power amplifier using quasi‐MMIC technology

ABSTRACTThis article presents an RLC matched power amplifier using quasi‐MMIC technology in the X‐band. The power amplifier consists of a GaN HEMT power device and several passive components including inductors, capacitors, resistors, and transmission lines using a silicon integrated passive device (IPD) process. The standard silicon process can drive the solution to cost down compared with conventional microwave monolithic integrated circuit (MMIC) technology. This technology using silicon IPDs provides small size matching networks close to MMIC dimensions. The input matching network using the RLC matched circuit is designed to obtain broadband characteristic and gain flatness. The dimensions of input and output silicon IPD are 1.5 mm × 1.2 mm and 1.9 mm × 2.2 mm, respectively, with a thickness of only 0.15 mm. The measured results show that the quasi‐MMIC power amplifier has a P3dB of more than 38.3 dBm with a drain efficiency of more than 51.2% in the frequency range from 8.2 to 10 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2803–2807, 2015

Modeling of Gan Hemt by Using an Improved K-Nearest Neighbors Algorithm

A novel black-box modeling method for field effect transistor (FET) based on an improved K-Nearest Neighbors algorithm is proposed in this paper. K-Nearest Neighbors algorithm, which has simple algorithm structure and high accuracy, has shown great potential in regression application. A Taylor series expansion method is employed in nonlinear elements modeling of FET to improve the physical meaning of black-box model. A GaN HEMT power device is used to demonstrate the proposed method. And the experimentation shows that the calculated results using improved K-Nearest Neighbors algorithm based model fit the measurement results well.

An Accurate I-V Model of Gan HEMT Power Device for the Application of Low Atmospheric Pressure

The characteristic variation of GaN HEMT device under low atmosphere pressure is studied in this research, which is a new challenge in the future. However, the variation is so small that cannot be represented by common current models. An accurate nonlinear current model is proposed in this study based on Angelov model to fit the small differences. The comparisons of simulated results based on the improved current model and measured results show that the improved model is accurate enough to describe the small differences and can improve the accuracy of nonlinear model of GaN HEMT device.

Reliability behavior of GaN HEMTs related to Au diffusion at the Schottky interface

AbstractThe Schottky contact on GaN HEMT power devices is a key element for high power performance and its long term reliability behavior. Up to now such GaN devices are still suffering very often by a leakage current increase during operation resulting in deteriorated transistor behavior. One reason for this problem is owing to insufficiently stable Schottky contacts based on NiAu metalisation. We analysed GaN HEMTs with different aging behaviors by means of HR‐TEM and EDX investigations. It could be shown that on transistors with increasing leakage current Au was found directly on the Schottky interface which may be responsible for the increase of the leakage current. Furthermore, there are strong indications that such Au is diffusing via the gate foot side wall Ni‐SiN interface towards the Schottky barrier. It is proposed that an additional metallic diffusion barrier may solve this aging problem. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A C-band high-dynamic range GaN HEMT low-noise amplifier

A C-band low-noise amplifier (LNA) is designed and fabricated using GAN HEMT power devices. The one-stage amplifier has a measured noise figure of 1.6 dB at 6 GHz, with an associated gain of 10.9 dB and IIP3 of 13 dBm. it also exhibits broadband operation from 4-8 GHz with noise figure less than 1.9 dB. The circuit can endure up to 31 dBm power from the input port. Compared to circuits based on other material and technology, the circuit shows comparable noise figure with improved dynamic range and survivability.