AlGaN/GaN on SiC Devices without a GaN Buffer Layer: Electrical and Noise Characteristics

• Main Authors: Justinas Jorudas, Artūr Šimukovič, Maksym Dub, Maciej Sakowicz, Paweł Prystawko, Simonas Indrišiūnas, Vitalij Kovalevskij, Sergey Rumyantsev, Wojciech Knap, Irmantas Kašalynas
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Micromachines
• Subjects: AlGaN/GaN; SiC; high electron mobility transistor; Schottky barrier diode; breakdown field; noise
• Online Access: https://www.mdpi.com/2072-666X/11/12/1131

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects. Fabricated Schottky barrier diodes (SBDs) demonstrated an ideality factor <i>n</i> at approximately 1.7 and breakdown voltages (fields) up to 780 V (approximately 0.8 MV/cm). Hall measurements revealed a thermally stable electron density at <i>N_2DEG</i> =1 × 10¹³ cm⁻² of two-dimensional electron gas in the range of 77–300 K, with mobilities <i>μ</i> = 1.7∙10³ cm²/V∙s and <i>μ</i> = 1.0∙10⁴ cm²/V∙s at 300 K and 77 K, respectively. The maximum drain current and the transconductance were demonstrated to be as high as 0.5 A/mm and 150 mS/mm, respectively, for the transistors with gate length <i>L_G</i> = 5 μm. Low-frequency noise measurements demonstrated an effective trap density below 10¹⁹ cm^-3eV^-1. RF analysis revealed <i>f_T</i> and <i>f_max</i> values up to 1.3 GHz and 6.7 GHz, respectively, demonstrating figures of merit <i>f_T</i> × <i>L_G</i> up to 6.7 GHz×µm. These data further confirm the high potential of a GaN–SiC hybrid material for the development of thin high electron mobility transistors (HEMTs) and SBDs with improved thermal stability for high-frequency and high-power applications.