Micro-Raman spectroscopy as a voltage probe in AlGaN/GaN heterostructure devices: Determination of buffer resistances

摘要

A time-resolved micro-Raman technique was developed to probe the transient voltage in the GaN buffer layer of AlGaN/GaN heterostructure devices. The transient potential distribution under Ohmic contacts of devices behaved like a capacitance-resistance coupled network, with a decrease in amplitude and phase shift of the potential as a function of operating voltage frequency. This phenomenon was used to extract a value of 0.6 MΩ/□ for sheet resistance of the A1N nucleation layer at the GaN/SiC interface from the characteristic RC value of the network. This demonstrates the effectiveness of this voltage probe technique as a non-invasive method of characterizing nucleation layers.