GaN HEMTs on low resistivity Si substrates with thick buffer layers for RF signal amplification and power conversion

Abstract

We report GaN high-electron-mobility transistors (HEMTs) with a thick (7.7 µm) GaN buffer on a Czochralski low resistivity Si (LRS) substrate. The GaN HEMTs exhibit high performance for both radio-frequency (RF) amplification and power conversion. The thick GaN buffer was grown by means of vacancy engineering, delivering a low dislocation density of ∼1.6 × 108 cm−2, contributing to suppressed RF signal coupling to the lossy Si substrate and a high vertical voltage blocking capability. For RF performance, GaN HEMTs with a 650 nm gate exhibit an fT/ fMAX value of 25.1/32.3 GHz and a maximum output power POUT of 2.2 W/mm at 4 GHz with a drain voltage VDS of 20 V, which is comparable with the performance of RF GaN HEMTs on a high-resistivity silicon substrate without the existence of the field plate. For power performance, the vertical breakdown voltage of the wafer is 1160 V, and the three-terminal lateral breakdown voltage is 885 V in a GaN HEMT with a gate-to-drain distance of 8 µm. The thick GaN layer on the LRS substrate scheme thus provides a compelling platform for monolithic integration of high-performance RF devices and high-voltage power devices.

Effect of High Al Content AlGaN Buffer Layer on the Properties of GaN‐on‐Silicon Materials

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GaN semiconductor materials have characteristics of large energy band gap, high electron saturation velocity, high breakdown field strength, and good thermal stability, which have broad application prospects in the preparation of radio frequency (RF) and power electronic devices. [1][2][3] Si substrates are inexpensive and easy to obtain different sizes (2-12 inches) and different types (n-type/p-type/high resistivity) of substrates, which can meet different epitaxial growth process requirements. Si-based GaN devices can be integrated with traditional Si-based devices on the same wafer, facilitating the formation of functional modules directly for terminal applications, [4][5][6] the growth of GaN-on-Silicon is receiving more and more attention.

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