Noise limitations of GaN lateral Schottky diodes for THz applications

Schottky diodes are key elements of RF and terahertz electronics. The design of the lateral Schottky with the contact directly to the side of the electron 2D channel in GaN/AlGaN system provides an advantage of extremely small capacitance and series resistance. The lateral Schottky devices based on high quality GaN/AlGaN heterostructures were grown by molecular beam epitaxy. The current voltage characteristics of fabricated diodes demonstrated small ideality factor of n=1.2-1.25, apparent barrier height Φ
_b
=(0.59-0.63) eV, and high reverse breakdown voltage exceeding 90 V. At low frequencies below 50 kHz the diodes demonstrated the superposition of 1/f and generation recombination noise. The spectral noise density of current fluctuations at small currents was proportional to the current squared. At high currents this dependence tended to saturate, which can be attributed to the influence of the series resistance. In comparison with regular GaN-based Schottky diodes fabricated in this work and reported in other publications, lateral Schottky diodes demonstrated the low frequency noise of the same or even smaller amplitude. Low level of noise makes GaN/AlGaN lateral Schottky diodes to be very promising devices for RF and terahertz applications.