3 GHz RF measurements of AlGaN/GaN transistors transferred from silicon substrates onto single crystalline diamond

Thomas Gerrer,Fouad Benkhelifa,Volker Cimalla,Rüdiger Quay,Heiko Czap,Christoph E Nebel,Patrick Waltereit,Stefan Müller,Thomas Maier

doi:10.1063/1.5127579

Thomas Gerrer, Fouad Benkhelifa + Show 7 more

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https://doi.org/10.1063/1.5127579

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Abstract

The integration of AlGaN/GaN thin film transistors onto diamond substrates enables the efficient dissipation of device heat, thus providing a boost in performance and reliability of current high-frequency GaN power amplifiers. In this paper, we show 3 GHz load-pull measurements of GaN transistors on silicon (Si) and single crystalline diamond (SCD) as fabricated by our recently presented direct low-temperature bond process. After the transfer onto SCD, the efficiency and output power are increased by 15%, which is explained by a calculated temperature difference of ∼100 K. In addition, the temperature between individual gate fingers is reduced such that the output power density (Pout) is independent of the amount of fingers. A drawback of our GaN epilayer is identified in the huge thermal resistance of the buffer layer so that the heat spreading performance of our technology is significantly impaired. Nevertheless, we demonstrate a large GaN-on-diamond output power of 14.4 W at a Pout of 8.0 W/mm.

Highlights

Thomas Gerrer,a) Heiko Czap, Thomas Maier, Fouad Benkhelifa, Stefan Müller, Christoph E
Between the thin film and the substrate, a buffer layer is introduced, which reduces crystalline defects, improves the electrical isolation, and mitigates thermomechanical stress. Since both the buffer layer and the substrate material limit the Gallium nitride (GaN) device performance, several ways are investigated to release the thin film after the growth and transfer it onto a different substrate
The good electrical isolation of diamond minimizes high-frequency electrical losses, and its outstanding thermal conductivity enables an efficient spreading of heat, generated locally within the GaN device channel

Summary

Introduction

Thomas Gerrer,a) Heiko Czap, Thomas Maier, Fouad Benkhelifa, Stefan Müller, Christoph E. We present detailed electrical measurements and thermal scitation.org/journal/adv simulations of RF transistors (3 GHz), which were transferred from Si onto SCD substrates.

Results

Conclusion