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

Area of Science:

• Materials Science
• Semiconductor Physics
• Electrical Engineering

Background:

• Aluminum Gallium Nitride/Gallium Nitride (AlGaN/GaN) heterostructures are crucial for high-power and high-frequency electronics.
• Traditional GaN-based devices often suffer from thermal management issues and trapping effects.
• Developing novel substrate materials is key to overcoming these limitations.

Purpose of the Study:

• To investigate the high-voltage, noise, and radio frequency (RF) performance of AlGaN/GaN devices grown on silicon carbide (SiC) without a GaN buffer.
• To evaluate the potential of this GaN-SiC hybrid material for improved thermal stability and reduced trapping.
• To assess the suitability of these devices for high-frequency and high-power applications.

Main Methods:

• Fabrication of Schottky barrier diodes (SBDs) and transistors using AlGaN/GaN on SiC.
• Characterization of device performance including breakdown voltage, ideality factor, drain current, and transconductance.
• Hall measurements to determine electron density and mobility at various temperatures.
• Low-frequency noise measurements to assess trap density.
• Radio frequency (RF) analysis to determine cutoff frequencies (fT and fmax).

Main Results:

• SBDs exhibited breakdown voltages up to 780 V (0.8 MV/cm) with an ideality factor of approximately 1.7.
• Thermally stable two-dimensional electron gas (2DEG) density (1x10^13 cm^-2) and high mobility (1.7x10^3 cm^2/V.s at 300K, 1.0x10^4 cm^2/V.s at 77K) were observed.
• Transistors achieved a maximum drain current of 0.5 A/mm and transconductance of 150 mS/mm (L=5 μm).
• Effective trap density was found to be below 10^19 cm^-3 eV^-1.
• RF analysis showed fT up to 1.3 GHz and fmax up to 6.7 GHz, with figures of merit (fT × L) reaching 6.7 GHz·μm.

Conclusions:

• The AlGaN/GaN on SiC hybrid material demonstrates excellent high-voltage and RF performance.
• The absence of a GaN buffer improves thermal management and reduces trapping effects.
• These devices show significant potential for advanced high-frequency and high-power electronic applications requiring enhanced thermal stability.