Uniform Growth of AlGaN/GaN High Electron Mobility Transistors on 200 mm Silicon (111) Substrate (original) (raw)
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physica status solidi (a), 2017
We investigated the effect of the Al content in the AlGaN buffer layer on the initial AlN nucleation layer, for AlGaN/ GaN high-electron-mobility transistors (HEMT), on a Si substrate. Reducing the Al content in the AlGaN layer decreased the surface pit density of the AlGaN layer, and increased the leakage current of the AlGaN/AlN/Si structures, but the crystal quality of the AlGaN layer was not changed by the Al content. The dislocation density of the GaN layer and the two-dimensional electron gas characteristics of the HEMT structures, were almost the same for the AlGaN buffer layer with differing Al content. However, the vertical-direction breakdown voltage (VDBV) was decreased at an Al content of 0.760 compared with other HEMT structures. In addition, the fluctuations of SLS layer were observed at an Al content of 0.760. The warpage and cracking of the HEMT structures were minimized at an Al content of 0.558. Based on these results, the VDBV of HEMT structures are not correlated with the VDBV of the AlGaN buffer layer. However, the VDBV of HEMT structures is affected by the surface pit density of the AlGaN buffer layer. In addition, the warpage of HEMTs on a Si substrate, can be controlled by the Al content of the AlGaN buffer layer.
Electrical characterization of AlGaN/GaN/Si high electron mobility transistors
Journal of Ovonic Research
AlGaN/GaN/Si HEMTs have been investigated using current-voltage-temperature and CDLTS measurements.As has been found from current voltage measurements, parasitic effects were revealed indicating the presence of traps in HEMT device. As a result, the origins of traps are determined from CDLTS experiments.
AlGaN/GaN high electron mobility transistors on Si(111) substrates
IEEE Transactions on Electron Devices, 2001
AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrates have for the first time been realized using organometallic vapor phase epitaxy (OMVPE). Using 1 -cm p-Si(111), these devices exhibited static output characteristics with low output conductance and isolation approaching 80 V. Under microwave rf operation, the substrate charge becomes capacitively coupled and parasitically loads these devices thereby limiting their performance. As a result, typical 0.3 m gate length devices show a 25 GHz cutoff frequency, with near unity max ratio and 0.55 W/mm output power. A small-signal equivalent circuit incorporating elements representing the parasitic substrate loading accurately models the measured S-parameters. Removal of the conductive substrate is one way to effectively eliminate this parasitic loading. Through backside processing, freestanding 0.4-mm HEMT membranes with no thermal management were demonstrated and exhibited a significant improvement in their max ratio up to 2.5 at the cost of lower and max along with an almost four-fold reduction of .
Japanese Journal of Applied Physics, 2010
We have fabricated AlGaN/GaN high-electron-mobility transistors (HEMTs) employing the proposed surface treatment by the deposition and removal of a SiO2 layer. The proposed treatment was applied before the Schottky contact formation. The output DC characteristics of the conventional and proposed devices were almost identical. The same threshold voltage indicates that the deposited SiO2 layer on the proposed device was completely eliminated. The proposed device decreased its leakage current by more than three orders compared with the conventional device and achieved a high breakdown voltage of 1300 V. The improvement in the blocking characteristics of the proposed device is due to the suppression of buffer leakage current, which is induced by the elimination of native oxide and the effect of N2O plasma on the surface of the AlGaN/GaN heterostructure.
Japanese Journal of Applied Physics, 2013
A normally-off AlGaN/GaN high-electron-mobility transistor (HEMT) with a recessed-gate structure fabricated by novel digital etching is reported. Digital etching consists of multiple cycles of oxidation and wet etching of the oxide, and has the merits of easy control of the recess depth and reduction of surface damage in comparison with conventional dry etching. However, in conventional digital etching, the oxidation process involves the possibility of undercutting. In the digital etching, a reactive ion etcher was used and recess etching without any undercut was confirmed. Normally-off operation and the improvement of transconductance were confirmed in an AlGaN/GaN HEMT fabricated by this technique.
Microwave and Optical Technology Letters, 2012
In this article, a gate recessed AlGaN/GaN high electron mobility transistor (HEMT) was developed using 4‐in. compound semiconductor process. We designed and fabricated four types of AlGaN/GaN HEMT to characterize the performance of devices. The effects of the gate recess depth and the device dimension of AlGaN/GaN HEMT are demonstrated. We present the scaling effect of the source‐gate and the drain‐gate enhancing the drain current and the transconductance. In addition, the current collapse was measured to estimate the trap effect in the surface and the buffer layer. Moreover, the comparison of RF performance of HEMT with different structure designs was performed. Based on these results, the optimization and the improvement of gate recessed GaN devices can be defined. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2103–2106, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27036
Effects of AlGaN Back Barrier on AlN/GaN-on-Silicon High-Electron-Mobility Transistors
Applied Physics Express, 2011
In this work, the effects of an AlGaN back barrier in the dc and RF performances of AlN/GaN high-electron-mobility transistors (HEMTs) grown on 100 mm Si substrates have been investigated. It is shown that the outstanding dc performance in highly scaled AlN/GaN-on-Si HEMTs can be fully preserved when introducing an AlGaN back barrier while significantly reducing the sub-threshold drain leakage current and enhancing the RF performance by the reduction of short-channel effects. Therefore, the AlN/GaN/AlGaN double heterostructure enables high-aspect-ratio devices generating extremely high current density, low leakage current, and high voltage operation. #
Electric Properties of AlGaN/GaN/Si High electron Mobility Transistors
Silicon, 2021
This work investigated the electrical properties in AlGaN/GaN/Si HEMTsgrown by molecular beam epitaxy. The electrical behavior have been investigated using by electric permittivity, modulus formalism and conductance measurements. As has been found from electrical conductance, dispersive behavior is related to barrier inhomogeneity and deep trap in barrier layer. On the other hand, the strain relaxation of charge transport is studied both permittivity and electric modulus formalisms.
Physica E: Low-dimensional Systems and Nanostructures, 2006
In order to grow high-quality GaN, we often choose sapphire as our substrates. However, silicon can be regarded as a new substrate due to its low cost and large wafer size. It is known that the difficulty of growing GaN on silicon is their large lattice mismatch (17%) and thermal mismatch (54%) between GaN and silicon. The usual process to reduce such mismatches is to grow an AlN layer as an intermediate layer. In this paper, we inserted a thin SiN layer between GaN and AlN to improve the quality of GaN, and the result showed that such thin SiN layer could greatly enhance the mobility of 2DEG formed at the interface of AlGaN and GaN. This suggests that it is possible to grow high-quality GaN on silicon as well as on sapphire with more studies of growth techniques.
AlGaN/GaN Heterostructures in High Electron Mobility Transistors
2018
AlGaN/GaN heterostructures are of high research and industrial interest for the production of high electron mobility transistors (HEMT) utilizing the two-dimensional electron gas (2DEG) induced at the interface due to polarization effects. In the current work, the effect of AlGaN thickness on 2DEG formation is under discussion. In particular, ultrathin layers of AlGaN (between 2-12 nm thick) are grown on top of GaN. Composition of these layers is studied and variations of surface potential are mapped using Kelvin probe force microscopy (KPFM) to see the evolution of the 2DEG formation in relation to layer thickness and stoichiometry. The obtained results allow concluding about critical thickness of AlGaN layer for the formation of continuous 2DEG at the AlGaN/GaN interface.