Influence of the Parameters of Schottky Barriers of AlGaN/GaN/SiC HEMT Transistors on the Phase Noise of Microwave Generators

Abstract

Microwave HEMT transistors based on gallium nitride (a novel wide-band-gap material) allow us to construct advanced radioelectronic systems. Therefore, the determination of the relation between the parameters of the transistor structure and the characteristics of microwave generators based on HEMT transistors is a relevant problem. The connection between the capacitance parameters of gate–drain Schottky barriers of AlGaN/GaN/SiC transistors and the phase noise power spectral density of microwave generators based on these transistors is analyzed. A set of power 6-finger transistors of the X band with a gate length of 0.25 μm, plated holes connecting the source region to the backside of the crystal, and field plates are studied. The C–V characteristics of most crystals are found to have a peak in the region of transition from enhancement to depletion in the measurements performed at frequencies f < 500 kHz. The height of this peak increases with a reduction in the measurement frequency. A rigid correlation between the height of the characteristic capacitance peak in the C–V curves and the power spectral density of the phase noise of the microwave generator based on the corresponding transistor crystal from the studied set is revealed. This correlation may be attributed to the presence of trap centers both in the barrier AlGaN layer and the structure interfaces.