Substantiation of buried two dimensional hole gas (2DHG) existence in GaN-on-Si epitaxial heterostructure

摘要

Gallium Nitride on Silicon (GaN-on-Si) devices feature a relatively thick epi buffer layer to release the stress related to the lattice constant mismatch between GaN and Si. The buffer layer is formed by several AlGaN-based transition layers with different Al contents. This work addresses the fun-damental question of whether two-dimensional hole gases (2DHGs) exist at those interfaces where the theory predicts a high concentration of a negative fixed charge as a consequence of the disconti-nuity in polarization between the layers. In this study, we demonstrate that the presence of such 2DHGs is consistent with the measured vertical Capacitance-Votage Profiling (CV) and Technology Caomputer-Aided Design (TCAD) simulation in the whole range of measurable fre-quencies (10 mHz-1 MHz). N-type compensating background donor included in the epi structure in the simulation deck proves to be crucial to explain the depletion region extension consistent with the CV experimental data. For the standard range of frequencies (1 kHz-1 MHz), there was no indi-cation of the presence of 2DHGs. A set of ultra-low frequency (10mHz-10Hz) measurements per-formed were able to reveal the existence of 2DHGs. The outcome of these ultra-low frequency experiments was matched with TCAD simulations which validated our theory,