Elsevier

Solid-State Electronics

Volume 183, September 2021, 108048
Solid-State Electronics

Analog performance of GaN/AlGaN high-electron-mobility transistors

https://doi.org/10.1016/j.sse.2021.108048Get rights and content

Highlights

  • Comparative analog performance of AlGaN/GaN HEMTs on silicon.

  • Reduce in analog parameters due Fermi potential change.

  • HEMTs are very attractive candidates for 5G applications.

  • Larger the channel length (L), greater efficiency is obtained.

  • Early voltage and intrinsic voltage gain increase is observed for longer channels.

Abstract

In this paper, the analog properties of advanced GaN/AlGaN High-Electron-Mobility Transistors (HEMTs) are studied as a function of temperature (T). The drain current, the threshold voltage, the transconductance and the output conductance are experimentally investigated under saturation operation. Moreover, important figures of merit for the analog performance, such as transconductance-over-drain current, Early voltage and intrinsic voltage gain are analyzed for different channel lengths in the temperature range of 25 °C till 200 °C. The results indicate that due to change in the Fermi potential, the analog parameters reduce with increasing T. Furthermore, the performance increase for longer channel devices is correlated directly with the lower drain electric field penetration.

Introduction

High frequency power over a wide bandwidth is essential for several applications, such as measurement and communication systems. High output power, wide bandwidth and high gain are requirements for such implementations. However, meet these criteria simultaneously are challenging [1].

Even though criteria are difficult to be met, High-Electronic-Mobility transistors do an excellent job when these needs are requested simultaneously. HEMTs are currently the first choice for high frequency, high power, high temperature or low noise applications. Its wide range of applications also includes computing, telecommunications, and instrumentation. During the last decade, AlGaN/GaN HEMTs have been intensively studied since their fundamental electrical properties make them very attractive candidates for 5G and millimeter-wave applications [2], [3], [4].

AlGaN and GaN are a wide band-gap material with high critical electric field, high mobility, and power density suitable for microwave and high-power applications [5]. One of the advantages of HEMT's behavior is that its structure generates a high-density 2D electron gas (2DEG) with improved carrier mobility in the heterointerface due to its great discontinuity of the conduction band and strong fields of piezoelectric and spontaneous polarization [6].

GaN device integration technology needs to be established for the next generation of power and RF devices, but current GaN technology based on non-Si substrates is costly and is handicapped by a limited wafer size. Migrating to a 200 mm Si platform and manufacturing devices using standardized fabrication tools are critical steps toward the uptake of GaN devices for RF applications [7].

As several application areas require the devices to operate at elevated temperatures, a proper of HEMT behavior with temperature dependency is highly important [8]. The channel length (L) directly impacts the channel resistance, and the drain current characteristics are affected by temperature [9]. In this paper, we used experimental results to investigate the analog performance (in saturation region) of AlGaN/GaN HEMTs with different channel lengths at different temperatures integrated on 200 mm Si wafers.

Section snippets

Experimental

The AlGaN/GaN HEMTs studied here are fabricated on 200 mm 〈1 1 1〉 Silicon wafers; a ~2 μm superlattice buffer is used. The GaN channel is 300 nm thick and the 15 nm barrier is made of Al0.25GaN. Devices were processed up to Metal 1 using an Au-free, gate-first process. More processing details can be found in [10].

Fig. 1 shows the AlGaN/GaN HEMT structure. The current–voltage characteristics were measured at different temperatures ranging between 25 °C and 200 °C on wafer in saturation operation

Results and discussion

The drain current (ID) and the transconductance (gm) versus gate voltage are shown in Fig. 2, Fig. 3. It is seen that for both parameters, the drain current and the transconductance decrease with increasing temperature. This was mainly attributed to the reduction of the mobility and electron velocity in the channel [12].

Threshold voltage represents the onset of significant drain current flow, which also depends on the channel length (Fig. 4). The HEMT weaker gate control at smaller channel

Conclusions

This paper reports an experimental study at different temperatures and channel lengths of AlGaN/GaN HEMTs on silicon. It was found that device analog parameters followed a pattern of increase or decrease according to the analyzed device channel size; longer channel devices have the higher Early voltage and higher intrinsic voltage gain.

In view of the temperature analysis, the same behavior could be perceived for all the figures-of-merit analyzed: an increase in the operating temperature yields

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.

Acknowledgments

This work has been performed within imec’s Partner Program on high-speed analog and RF devices.

Luis Felipe de Oliveira is a brazilian Control and Automation engineer graduated in 2019 at Instituto de Ciência e Tecnologia - Câmpus de Sorocaba. Since the beginning of his graduation, he started his academic life in scientific initiations in semiconductor devices and transistors area. Luis was awarded a scientific initiation scholarship for two FAPESP projects in microelectronics area and was considered the best student in 2019 Control and Automation engineer class. Luis is currently a

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