Enhanced irradiance sensitivity of 4H-SiC based ultraviolet sensor introducing laterally gated Al/SiO2/SiC tunnel diode structure with low gate bias

Abstract

A laterally gated Al/SiO2/SiC structure composed of an inner circular tunnel diode (TD) and an outer annular TD is investigated in this work to demonstrate the improved ultraviolet (UV) response in comparison with a single metal–oxide–semiconductor (MOS) TD or a conventional photodiode scheme. The current of the inner TD (ID) can interrelate with the bias of the outer TD (VG) against the voltage of inner TD (VD). This coupling effect will increase if the outer TD is negatively biased, thereby augmenting the optical current ratio and the responsivity. The lateral flow of holes is determined by the variation of the intermediate hole barrier between the inner and outer TDs. Once the hole potential at the outer TD overtops that at the inner TD, photogenerated holes from the outer TD can flow to the inner TD. Moreover, the suggested coupled TD design exhibits distinct increments in photocurrent under various illumination levels because of the coupling effect. For VD = −1.5 V and VG = −2 V, the optical current ratio reaches 12 841 at 303 K, and the obtained responsivity attains 0.0052 at 383 K with a light irradiance of 50 mW/cm2. Hence, the laterally gated MOS device can operate at elevated temperatures and heightened optical intensities, making it a promising UV sensor with enhanced irradiance sensitivity.