Optimization of VLS Growth Process for 4H-SiC P/N Junctions

Abstract

P/N junctions have been fabricated with N+ commercial 4H-SiC substrate on which Vapor-Liquid-Solid (VLS) selective epitaxy was used to create a localized p-type doping. The influence of the carrier gas nature (argon or hydrogen) has been investigated in terms of quality of the growth morphology, deposit thickness and electrical behavior of the P/N junction. Distinct results have been observed with a clear improvement when using VLS selective epitaxy under hydrogen.

Further optimization of VLS localized epitaxy for deeper 4H-SiC p-n junctions

“…This result confirms the trend that was already observed in a preliminary study . It is possible that during the manufacturing process, the front side metallic contacts were not patterned precisely enough, and that metallic residues could be present on the n‐type lateral sides of the wells.…”

“…Questions about the possible complex RF induction phenomena within the liquid phase, and the actual temperature of this liquid phase during the VLS process remain. Concerning the electrical behavior of p–n junctions, the improved results obtained confirm the trend already observed in previous works . The measured low‐voltage reverse leakage current density is lower than previously, thanks to our progress in surface preparation and ICP etch step optimization.…”

“…To start this study, the best growth conditions previously identified were chosen as the starting point: plateau duration of 15 min at 1100 °C, under 10 slm H 2 flow and 1 sccm propane flow. Then, the impact of growth duration was tentatively studied between 15 and 75 min, with the aim to increase the deposit thickness with time.…”

“…In this previous work, efforts were focused on the optimization of both the localization process and the VLS growth parameters. This investigation began with the study of the influence of the carrier gas (Ar vs. H 2 ) . Dramatic improvement was obtained with H 2, as compared to Ar, in terms of surface morphology.…”

Very High Sustainable Forward Current Densities on 4H-SiC p-n Junctions Formed by VLS Localized Epitaxy of Heavily Al-Doped p⁺⁺ Emitters

“…To solve this problem, VLS localized epitaxy has been previously proposed by some of the authors as an alternative to implement deeper localized Al doping at high concentrations [3,4]. Further works have resulted in the improvement of localized VLS process, yielding optimized structural morphology [5], preserving a threshold voltage of ~ 3 V in forward bias, value predicted by the classical theory, on a 4H-SiC p-n junction, and eliminating the need of high temperature post-growth annealing (previously ~1700°C) [6]. To the best of our knowledge, this electrical behaviour has never been obtained before with such low temperature doping process (1100°C).…”