Performance enhancement of normally off InAlN/AlN/GaN HEMT using aluminium gallium nitride back barrier☆

https://doi.org/10.1016/j.compeleceng.2022.107695Get rights and content

Highlights

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    DC and SCEs performances are investigated for enhancement-mode HEMT with variation of AlGaN back barrier thickness.

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    2D Sentaurus TCAD hydrodynamic simulation model are calibrated with experimental results.

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    Threshold voltage is increased and gate leakage current reduced.

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    AlGaN back barrier device featured better electrostatic control and significant improvement in short channel effects.

Abstract

In the present work, we have studied the influence of Aluminium Gallium Nitride (AlGaN) back-barrier (BB) thickness on the direct current (DC) and short channel effects (SCEs) of lattice matched In0.17Al0.83N/AlN/GaN Gate-Recessed normally off high electron mobility transistor (HEMT) grown on silicon carbide substrate. The extensive simulations are done by the 2Dimenssional synopsis TCAD by means of Hydrodynamic (HD) mobility model and calibrated with the experimental result. The DC performance of the device has been studied using the simulations for different BB thickness (tbb) and a comparison was made with regard to the device without BB for gate length (Lg) 50 nm and 75 nm. The result indicates that use of AlGaN BB has several advantages like improving the SCEs, reducing leakage current and resulting higher threshold voltage (Vth). Therefore the implementation of AlGaN BB in related devices perhaps another way out for high power and digital switching purpose.

Introduction

Now a day's nitride related HEMTs have appeared as a prospective contender for high-power and high-frequency appliances. In this respect AlGaN/GaN devices have usually led this field. However the uniqueness of In0.17Al0.83N/GaN projected by Kuzmik has become a smart substitute with respect to usually used AlGaN/GaN based devices in recent time [1], [2], [3], [4]. The In0.17Al0.83N/GaN with several structural advantages compare to AlGaN barrier GaN structures i.e. lattice matching In0.17Al0.83N with GaN and proposed device can fewer susceptible to relaxation related deterioration and having more stable and reliable [5]. Large polarization discontinuation available in between the boundary of InAlN front barrier and GaN channel outcome in enhanced confinement of carrier and lead to higher two-dimensional electron gas (2DEG) in the channel, which can prevail over the confines of SCEs [1]. The proposed device also shows a step up in microwave performances by the reduction in Lg and the thickness of InAlN barrier shrinking [6]. Ostermaier proposed InAlN/GaN E-HEMT structure with cut off frequency (fT) of 33 GHz [7], and the R. Wang reported the device structure having the transconductance (gm) of 800 ms/mm and also current density of 1.9 A/mm [8]. Despite of these results, SCEs has been noted as consecutive reduction of Lg to get the high frequency performances. It has been observed that for Lg below 100 nm a thin front barrier of below 3 nm is necessary to prevail over the SCEs. However more reduction in tbb of the InAlN barrier guides to enlarged gate leakage current and decrease in 2DEG [9]. In order to surmount these difficulties of scaling without lacking the device characteristics, insertion of BB can be an utmost alternate. Few researchers have considered the result of BB to get the increased GaN based device performances [10], [11], [12], [13], [14]. Few researchers have analyzed the impact of AlGaN BB [15], [16], [17], [18], [19], most of them attention on the depletion mode devices. As per literature assessment for the first time the AlGaN BB observed by Adak group in E-HEMT InAlN/GaN based devices [18,19]. Very few groups have studied different electrical parameters varying AlGaN BB thickness of GaN based depletion mode HEMT [20,21]. In the present work we have studied the influence of tbb on various electrical performances of the proposed E-HEMT devices, such as Vth, subthreshold slope (SS), drain induced barrier lowering (DIBL), transfer characteristics, gate leakage current, for Lg 50 nm and 75 nm by using 2D Sentaurus TCAD HD mobility simulation.

The rest of this paper is organized as follows: Section 2 shows the device description; Section 3 explains the simulation model calibration and experimental comparison; Section 4 gives the results and discussion; and lastly, we illustrate the conclusion and make suggestion for future scope in Section 5.

Section snippets

Device description

Figs. 1 and 2 described the cross section of In0.17Al0.83N/AlN/GaN Gate-Recessed E-HEMTs grown on SiC substrate; 4.8 nm and 1 nm thick InAlN and AlN has been used as front barrier and spacer respectively. Previous one with GaN as buffer and Lg 150 nm whereas the proposed one is with variable tbb from 150 nm to 400 nm along with 30 nm UID GaN channel (Tc) and having Lg of 50 nm and 75 nm, respectively. SiN has been used as a passivation layer for both the devices. Platinum/Gold metal is used to

Simulation model calibration and experimental comparison

Table 1 listed the properties of In0.17Al0.83N and GaN compound materials. Numerical modeling has been set up by Technological CAD tool [24]. The simulation has been carried out using HD mobility model. Further more important properties are in use into considerations for example bandgap narrowing, doping dependent mobility at high electric fields, spontaneous polarizations and varying effective mass. Fig. 3 shows the transfer characteristics of the InAlN/AlN/GaN E-HEMT structure (Fig. 1)

Results and discussion

Figs. 4 and 5 represents the Id vs Vg of the InAlN/AlN/GaN Gate-Recessed E-HEMT (Fig. 2) with different AlGaN tbb, for Lg of 75 nm and 50 nm, respectively. From the numerical modeling data it is found that with enhance in tbb the drain current decreases and moreover the current decreases to 26% and 24% for the AlGaN tbb 400 nm for the Lg 75 nm and 50 nm, respectively. The decreased in drain current (Id) density is mainly due to decrease in sheet charge density with enhance in tbb at the surface

Conclusion

This report systematically explores the consequence of tbb on the InAlN/AlN/GaN Gate-Recessed normally off HEMT. 2D Sentaurus TCAD simulation result confirms that the introduction of AlGaN BB structure has a great impact on SCE parameters. It has the advantage of reducing the gate leakage current by more than 10 times as compare to device without BB. Additionally, introduction of AlGaN BB is a new approach to controlling the DIBL and SS which in turn improves the SCEs. The shift in Vth towards

CRediT authorship contribution statement

Nisarga Chand: Methodology, Writing – original draft. Sarosij Adak: Methodology, Conceptualization, Writing – review & editing, Supervision. S.K. Swain: Writing – review & editing. Sudhansu Mohan Biswal: Investigation, Validation. A. Sarkar: Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

S. Adak, S.K. Swain and S. M. Biswal would like to express their thanks to BBIT Kolkata, and SIT Bhubaneswar correspondingly, for their assistance to carry out the work. Also authors express their thanks to Prof. Hafizur Rahaman IIEST Shibpur for technical support and important scientific discussion.

Nisarga Chand is presently serving as an Assistant Professor of ECE in Adamas University, West Bengal. He is pursuing his PhD from MAKAUT, W.B. He completed M.Tech from MAKAUT, W.B. His research interest is in Nano Electronics & Device engg. He has more than 10 years of teaching experience. He is a Professional Member of ISIE, India.

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      2023, SSRN

    Nisarga Chand is presently serving as an Assistant Professor of ECE in Adamas University, West Bengal. He is pursuing his PhD from MAKAUT, W.B. He completed M.Tech from MAKAUT, W.B. His research interest is in Nano Electronics & Device engg. He has more than 10 years of teaching experience. He is a Professional Member of ISIE, India.

    Sarosij Adak is presently serving as an Associate Professor of ECE in BBIT Kolkata, W. Bengal. He completed his M.Tech from WBUT and PhD in Engg from IIEST Shibpur, W.B. His research interest is in Semiconductor devices modeling and simulation study. He has more than 10 years of teaching and research experience. S. K. Swain is presently serving as an Associate Professor of ECE in Silicon Institute of Technology, Bhubaneswar, Odisha. He completed his M.Tech from BPUT, Odisha and PhD in Engg (Semiconductor Devices) from Jadavpur University. His research interest is in Nano Electronics & Device engg. He has almost 15 years of teaching experience and 3 years of research experience.

    Sudhansu Mohan Biswal is presently serving as an Associate Professor of ECE in Silicon Institute of Technology, Bhubaneswar, odisha. He completed his M.Tech from BPUT, Odisha and PhD in Engg from MAKAUT, W.B. His research interest is in Semiconductor devices modeling and simulation study. He has more than 16 years of teaching and 7 years of research experience.

    A. Sarkar is presently serving as a Professor of Electronics & Communication Engineering in Maulana Abul Kalam Azad University of Technology, West Bengal. He completed his PhD from Jadavpur University. His current research interest VLSI & Microelectronics.

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    This paper is for special section VSI-mnds. Reviews were processed by Guest Editor Dr. A. Sarkar and recommended for publication.

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