2D TCAD Sentaurus simulations based on Drift-Diffusion transport are performed to identify the modeling parameters that crucially affect the reliability characteristics of AlGaN/GaN HEMT devices, ...demonstrated by their effects on the gate leakage characteristic. The behavioural nature and impact of each parameter on the leakage performance is discussed. Schottky gate tunneling and trapping effects within the structure are two major reliability issues that modulate the leakage characteristic. Hence, their contributions are precisely modeled. A simulation methodology is presented to recognize the relative control of individual parameters on distinct regions of the leakage characteristic. This modeling approach is demonstrated for a GaN HEMT technology and can be further applied to facilitate reliability comparisons across different device technologies. This validates TCAD simulation to be an effective aiding tool in reviewing and interpreting GaN HEMT reliability performance and design choices.
•2D TCAD Drift-Diffusion simulations performed to identify impact on gate leakage•Parameters crucially affecting reliability of GaN HEMTs are identified.•A simulation methodology recognizes relative parameter control over IG-VG.•Facilitates reliability and performance comparisons across device technologies
Fluorine ion migration in normally-off AlN/GaN HEMTs fabricated by fluorine ion plasma implantation technology is evidenced. Devices under test are co-integrated into the OMMIC commercial ...D006GH/D01GH MMIC process, providing fluorine-free normally-on HEMTs. Gate reverse bias step-stress experiment at a drain fixed voltage of 0 V, carried out as well on normally-on ones as on normally-off ones, shows a permanent negative shift in the threshold voltage Vth of normally-off devices only. Vth degradation is starting at a VGS,stress of −8 V, with a negative shift from 0 V to −0.4 V at VGS,stress = −30 V, while the transconductance gm and gm,max remains unchanged prior to breakdown that occurred at VGS,stress ranging between −26 and −32 V. Since the positive threshold voltage of these devices is induced by F-ions dose and position, the above result suggests a possible drift of F-ions away from the 2DEG channel. A field-assisted migration mechanism of fluorine ions is proposed and supported by the absence of Vth degradation in fluorine-free normally-on devices.
This paper describes an approach for the evaluation of reliability of a heterogeneous integration of gallium nitride (GaN) and gallium arsenide (GaAs) RF power monolithic microwave integrated ...circuits (MMICs) in a Fan-Out Wafer-Level Packaging (FOWLP) configuration. The methodological approach presented here combines accelerated ageing tests and physical simulations to assess the package reliability. Multiple challenges are encountered in the integration and reliability of GaN and GaAs chips in FOWLP. The limiting factors in the GaN integration are the thermal dissipation due to the high power and the thermomechanical behavior of the package. To apprehend such behaviors, test structures have been especially designed. A structure is dedicated to the evaluation of the package thermal resistance (Rth). The output characteristic comes from a transistor in a common source configuration, with the drain shorted and the gate voltage close to zero to allow almost no current in the transistor. Rth values are calculated via measurements of the gate resistance and the use of abacus of equivalence. Moreover, thermo-mechanical stress sensors (based on GaN active zone) are manufactured to evaluate the deformation during assembly and operating life. The sensors can be assimilated to active resistances along the four edges of the die. They have been measured on wafer to serve as reference. By measuring them, the sheet resistance can be extracted and the thermal coefficients calculated. Both structures are encapsulated in FOWLP. To complete the study, thermomechanical simulations will be made. It will permit to numerically evaluate the limits of the System in Package (SiP) when modelled with the in-situ viscoelastic properties of materials of the package.
•Selective sublimation of p-GaN is developed to fabricate enhancement-mode HEMTs.•AlGaN regrowth drastically reduces access resistances in enhancement-mode HEMTs.•Sublimation and regrowth are ...combined to co-integrate E/D-mode GaN HEMTs.
We report on the fabrication of an enhancement mode p-GaN/AlN/GaN high electron mobility transistor with selective area sublimation under vacuum of the p-GaN cap layer. The GaN evaporation selectivity is demonstrated on the thin 2 nm AlN barrier layer. Furthermore, the regrowth of AlGaN is a major key to increase the maximum drain current in the transistors and enables the co-integration with depletion mode devices.
This paper deals with the deep characterization of a novel electrical parasitic effect in AlGaN/GaN technology so called "electrical runaway mechanism." It is characterized by an anomalous gate ...current behaviour. Electrical measurements versus temperature show that the runaway mechanism threshold is temperature independent on the contrary to the gate current progression as a function of VDS. Optoelectrical measurements show that the physical mechanism inducing the runaway mechanism occurs below the gate area. Then, reliability aging tests performed in the frame of a 0.5-μm GaN technology present the runaway mechanism as a wear out mechanism. Finally, the runaway mechanism has been associated with tunnel conduction through gate metal and AlGaN layer.
