Investigating two−stage degradation of threshold voltage induced by off−state stress in AlGaN/GaN HEMTs

2021 ◽  
Author(s):  
Yu-Shan Lin ◽  
Yi-Lin Chen ◽  
Ting-Chang Chang ◽  
Fong-Min Ciou ◽  
Qing Zhu ◽  
...  
Keyword(s):  
Threshold Voltage ◽  
Gate Dielectric ◽  
Impact Ionization ◽  
Gate Insulator ◽  
High Electron ◽  
Electron Hole ◽  
Stress Threshold ◽  
Temperature Impact ◽  
Electron Transistors ◽  
State Stress

Abstract In this work, a two-step degradation phenomenon in D-mode Si3N4/AlGaN/GaN metal-insulator-semiconductor high−electron−transistors (MIS−HEMT) is discussed systematically. During off−state stress, threshold voltage shifts positively for a short duration, and is followed by a negative shift. In contrast, the off−state leakage continues to decrease throughout the entire stress. Results of varied measurement conditions indicate that carrier trapping at different regions dominates this phenomenon. It is interesting that under a large lateral electric field, electron−hole pairs are generated and will then be trapped at the gate dielectric layer. Furthermore, when increasing the stress temperature, impact ionization due to carriers from the gate electrode becomes more severe. Finally, devices with different gate insulator (GI) thicknesses are performed to verify the physical model of the degradation behavior.

The Dependence of Carrier Distribution on Gate Capacitance of α-IGZO TFTs

2014 ◽  
Vol 598 ◽  
pp. 361-364 ◽  
Author(s):  
Chih Chieh Hsu ◽  
Chien Hsun Wu
Keyword(s):  
Threshold Voltage ◽  
Computer Aided Design ◽  
Gate Dielectric ◽  
Oxide Thin Film ◽  
High Electron ◽  
Indium Gallium Zinc Oxide ◽  
Gate Bias ◽  
Carrier Distribution ◽  
Fully Depleted ◽  
Gate Capacitance

The capacitance-voltage (C–V) characteristics of inverted staggered amorphous indium–gallium–zinc-oxide thin film transistors (α-IGZO TFTs) with various dimensions are investigated by physics-based technology computer aided design (TCAD) simulation. For gate bias lower than the threshold voltage of the TFT, the electrons in the channel region are nearly fully depleted. It causes that the total gate capacitance is determined by the overlap region of gate, α-IGZO, and source/drain metals. When the applied gate bias is higher than the threshold voltage, the high electron density channel with density of ~6 × 1017 cm-3 and thickness of ~3-4 nm is observed near the interface of α-IGZO and gate dielectric. It results that the total gate capacitance is dominated by the gate to channel overlap. Quantitative analysis of the carrier distribution and energy band structures are utilized to study the physical mechanism underlying the C–V characteristics of the α-IGZO TFTs.

scholarly journals Comprehensive Research of Total Ionizing Dose Effects in GaN-Based MIS-HEMTs Using Extremely Thin Gate Dielectric Layer

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2175
Author(s):  
Sung-Jae Chang ◽  
Dong-Seok Kim ◽  
Tae-Woo Kim ◽  
Jung-Hee Lee ◽  
Youngho Bae ◽  
...  
Keyword(s):  
Dielectric Layer ◽  
Radiation Effects ◽  
Gate Dielectric ◽  
Stress Measurement ◽  
Gate Insulator ◽  
Dose Effect ◽  
High Electron ◽  
Total Ionizing Dose ◽  
Γ Ray ◽  
Rf Performance

The device performance deterioration mechanism caused by the total ionizing dose effect after the γ-ray irradiation was investigated in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) for a 5 nm-thick SiN and HfO2 gate dielectric layer. The γ-ray radiation hardness according to the gate dielectric layer was also compared between the two different GaN-based MIS-HEMTs. Although HfO2 has exhibited strong tolerance to the total ionizing dose effect in Si-based devices, there is no detail report of the γ-ray radiation effects in GaN-based MIS-HEMTs employing a HfO2 gate dielectric layer. The pulsed-mode stress measurement results and carrier mobility behavior revealed that the device properties not only have direct current (DC) characteristics, but radio frequency (RF) performance has also been mostly degraded by the deterioration of the gate dielectric quality and the trapped charges inside the gate insulator. We also figured out that the immunity to the γ-ray radiation was improved when HfO2 was employed instead of SiN as a gate dielectric layer due to its stronger endurance to the γ-ray irradiation. Our results highlight that the application of a gate insulator that shows superior immunity to the γ-ray irradiation is a crucial factor for the improvement of the total ionizing dose effect in GaN-based MIS-HEMTs.

A correlation of CL emissions from Penrith sandstone with elemental distributions obtained by simultaneous SEM-CL and EDS analysis

1995 ◽  
Vol 53 ◽  
pp. 392-393
Author(s):  
Paul J. Wright
Keyword(s):  
Optical Microscope ◽  
Electron Gun ◽  
High Electron ◽  
Collection System ◽  
Electron Hole ◽  
Depositional Processes ◽  
Eds Analysis ◽  
Distribution Mapping ◽  
Backscattered Electron ◽  
Electron Imaging

Most industrial and academic geologists are familiar with the beautiful red and orange cathodoluminescence colours produced by carbonate minerals in an optical microscope with a cold cathode electron gun attached. The cement stratigraphies interpreted from colour photographs have been widely used to determine the post depositional processes which have modified sedimentary rock textures.However to study quartzose materials high electron densities and kV's are necessary to stimulate sufficient emission. A scanning electron microscope with an optical collection system and monochromator provides an adequate tool and gives the advantage of providing secondary and backscattered electron imaging as well as elemental analysis and distribution mapping via standard EDS/WDS facilities.It has been known that the incorporation of many elements modify the characteristics of the CL emissions from geological materials. They do this by taking up positions between the valence and conduction band thus providing sites to assist in the recombination of electron hole pairs.

Impact ionization, recombination, and visible light emission in AlGaAs/GaAs high electron mobility transistorsa)

1991 ◽  
Vol 70 (1) ◽  
pp. 529-531 ◽  
Author(s):  
Enrico Zanoni ◽  
Alessandro Paccagnella ◽  
Pietro Pisoni ◽  
Paolo Telaroli ◽  
Carlo Tedesco ◽  
...  
Keyword(s):  
Visible Light ◽  
Electron Mobility ◽  
Impact Ionization ◽  
Light Emission ◽  
High Electron ◽  
High Electron Mobility ◽  
Visible Light Emission

Effect of High Temperature Forming Gas Annealing on Electrical Properties of 4H-SiC Lateral MOSFETs with Lanthanum Silicate and ALD SiO2 Gate Dielectric

2018 ◽  
Vol 924 ◽  
pp. 482-485
Author(s):  
Min Seok Kang ◽  
Kevin Lawless ◽  
Bong Mook Lee ◽  
Veena Misra
Keyword(s):  
Threshold Voltage ◽  
Interfacial Layer ◽  
Field Effect ◽  
Lanthanum Oxide ◽  
Gate Dielectric ◽  
High Mobility ◽  
High Threshold ◽  
Field Effect Mobility ◽  
The Impact ◽  
Lanthanum Silicate

We investigated the impact of an initial lanthanum oxide (La2O3) thickness and forming gas annealing (FGA) conditions on the MOSFET performance. The FGA has been shown to dramatically improve the threshold voltage (VT) stability of 4H-SiC MOSFETs. The FGA process leads to low VTshift and high field effect mobility due to reduction of the interface states density as well as traps by passivating the dangling bonds and active traps in the Lanthanum Silicate dielectrics. By optimizing the La2O3interfacial layer thickness and FGA condition, SiC MOSFETs with high threshold voltage and high mobility while maintaining minimal VTshift are realized.

High Voltage AlGaN/GaN Heterojunction Transistors

2004 ◽  
Vol 14 (01) ◽  
pp. 225-243 ◽  
Author(s):  
L. S. McCarthy ◽  
N-Q. Zhang ◽  
H. Xing ◽  
B. Moran ◽  
S. DenBaars ◽  
...  
Keyword(s):  
Drain Current ◽  
Gate Insulator ◽  
Threading Dislocation ◽  
High Electron ◽  
Resistive Load ◽  
Power Switching ◽  
Field Plate ◽  
Switching Power ◽  
Dislocation Densities ◽  
Extrinsic Base

The use of AlGaN / GaN HEMTs and HBTs for switching power supplies is explored. With its high electron velocities and breakdown fields, GaN has great potential for power switching. The field-plate HEMT increased breakdown voltages by 20% to 570V by reducing the peak field at the drain-side edge of the gate. The use of a gate insulator is also investigated, using both JVD SiO 2 and e-beam evaporated SiO 2 to reduce gate leakage, increasing breakdown voltages to 1050V and 1300V respectively. The power device figure of merit (FOM) for these devices: [Formula: see text], is the highest reported for switching devices. To reduce trapping effects, reactively sputtered SiN x, is used as a passivant, resulting in a switching time of less than 30 ns for devices blocking over 110V with a drain current of 1.4A under resistive load conditions. Dynamic load results are also presented. The development of HBTs for switching applications included the development of an etched emitter HBT with a selectively regrown extrinsic base. This was later improved upon with the selectively regrown emitter devices with current gains as high as 15. To improve breakdown in these devices, thick GaN layers were grown, reducing threading dislocation densities in the active layers. A further improvement included the use of a bevelled shallow etch and a lateral collector design to maximize device breakdown.

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