Browsing by Subject "High-electron-mobility transistors (HEMTs)"

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Open Access
Fast unveiling of Tmax in GaN HEMT devices via the electrical measurement-assisted two-heat source model
(IEEE, 2022-04-07) Koçer, Hasan; Durna, Yılmaz; Güneş, Burak; Tendürüs, Gizem; Bütün, Bayram; Özbay, Ekmel
Gallium nitride (GaN) high-electron-mobility transistor (HEMT) devices, which have wide application potential from power amplifiers to satellite, need to be thoroughly examined in terms of reliability in order to benefit the superior intrinsic properties of the device. The most critical parameter in the device reliability is the hotspot, or Tmax , which occurs somewhere on the subsurface and along the channel of the GaN HEMT, which is optically inaccessible due to optical path disability. Therefore, the Tmax value is underestimated in optical measurements, such as the thermographic IR and Raman methods. With 3-D electrothermal simulations, Tmax is obtained close to reality, but it requires a huge computation load and the complex modeling of semiconductor device physics. In 2-D or 3-D thermal simulations that do not use electrothermal simulations, since the self-heating is mostly modeled with a single heat source, neither the correct Tmax value is obtained nor the effect of bias conditions is considered. To address the aforementioned shortcomings, a hybrid method is demonstrated, which exploits the electrical measurements of GaN HEMT, which RF and reliability engineers often and easily do. It is demonstrated that Tmax can be determined quickly and close to the electrothermal simulations in a GaN HEMT device with a two-heat source method and finite element analysis (FEA) hybrid interaction with respect to various bias conditions. Moreover, the impact of the knee voltage is investigated with different knee-detection techniques. The proposed method provides GaN HEMT reliability engineers with an easy-to-implement alternative to reveal the hotspot location and the value.
Open Access
Improved Tmax estimation in GaN HEMTs using an equivalent hot point approximation
(IEEE, 2020) Odabaşı, Oğuz; Akar, Mehmet Ömer; Bütün, Bayram; Özbay, Ekmel
In this article, heat generation distribution and maximum device temperature of gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) are investigated by using the 2-D electrothermal and finite-element method (FEM) simulations. Devices with different gate lengths and source-to-drain spacing are investigated. It is observed that the maximum device temperature (TMAX) depends on the drain-to-source spacing and is almost independent of the gate length and that the assumption of a uniform heat generation region, under the gate, is not accurate; this is contrary to conventional calculation methods. Moreover, based on the results, a new approximation is proposed to use in the FEM simulations that can estimate TMAX more accurately. This method does not require physics-based technology computer-aided design (TCAD) simulations and can work with a low mesh density. The performance is compared with prior methods.
Open Access
Normally-off p-GaN gate InAlN/GaN HEMTs grown on silicon substrates
(SPIE, 2019-02) Gülseren, Melisa Ekin; Bozok, Berkay; Kurt, Gökhan; Kayal, Ömer Ahmet; Öztürk, Mustafa; Ural, Sertaç; Bütün, Bayram; Özbay, Ekmel
A normally-off InAlN/GaN high electron mobility transistor (HEMT) on Si substrate with a p-GaN gate is reported. Devices are fabricated on two different epitaxial structures, one containing a high resistive GaN buffer layer and one containing an AlGaN back-barrier, and the threshold voltage, drain current density, and buffer leakage current are compared. With the epitaxial structure containing a high resistive GaN layer, normally-off operation with a threshold voltage of +0.5 V is achieved. The threshold voltage is further increased to +2 V with the AlGaN back-barrier, and the buffer leakage current was improved by over an order of magnitude.