In-situ surface preparation of nominally on-axis 4H-SiC substrates

Abstract

A study of the in-situ surface preparation has been performed for both Si-and C-face 4H-SiC nominally on-axis samples. The surface was studied after etching under C-rich, Si-rich and under pure hydrogen ambient conditions at the same temperature, pressure and time interval using a hot-wall chemical vapor deposition reactor. The surfaces of all the samples were analyzed using optical microscopy with Normarski diffractional interference contrast and atomic force microscopy with tapping mode before and after in-situ etching. Polishing related damages were found to be removed under all etching conditions, also the surface step structure was uncovered and a few defect-selective etch pits were observed. For the Si-face sample, the best surface morphology was obtained after Si-rich etching conditions with more uniform and small macro-step height which resulted in the lowest surface roughness. For the C-face sample the surface morphology was comparable under all etching conditions and not much difference was found except for the etching rate. Si droplets were not observed under any etching conditions.

Initial stages of growth and the influence of temperature during chemical vapor deposition of sp2-BN films

“…Prior to the thin film deposition both type of substrates were in situ pretreated, where an AlN buffer layer was formed on -Al 2 O 3 by nitridation at the applied growth temperature using ammonia at a total concentration 10 % in hydrogen during 10 minutes 24 or by the introduction of silane into the reactor at the temperature of 950 °C in order to improve the 6H-SiC substrate surface morphology 29 .…”

Quasi-free-standing monolayer and bilayer graphene growth on homoepitaxial on-axis 4H-SiC(0 0 0 1) layers

“…In the case of on-axis epitaxy, we have observed that in-situ surface preparation of the substrate and growth in slightly Si-rich environment together with slightly higher growth temperature plays a key role in the replication of the substrate polytype into the epilayer. Surface preparation under such conditions reveals more uniform surface step structure mainly composed of large steps that are usually about 10-40 nm and small steps that are 0.5-1 nm [25]. The small steps originate from threading screw dislocations intersecting the surface while the large steps are related to small unintentional off-cut in the substrate and surface step-bunching on the Si-face.…”

Concentrated Chloride-Based Epitaxial Growth of 4H-SiC

“…The ramp up conditions were modified as well as compared to the process run at high carrier flow and high pressure. Therefore a smoother surface could be obtained by adding SiH 4 during ramp up, the amount to be used depended on the substrate off-angle: a small amount of 20 sccm for 8° off-axis substrates, 100 sccm for on-axis substrates with a subsequent 10 minutes etching at the growth temperature [16,17]. of 3 as is usually needed for the f the 8° off-axis epilayers grown at 55 μm/h is very good, as confirm by provided the n-axis samples confirmed the epitaxial layer to be 100% 4H-SiC of very high crystalline quality.…”