Ge Assisted SiC Epitaxial Growth by CVD on SiC Substrate

Abstract

This paper presents the results obtained after chemical vapor deposition of SiC with the addition of GeH4gas to the classical SiH4+C3H8precursor system. Epitaxial growth was performed either on 8°off-axis or on-axis 4H-SiC substrate in the temperature range 1500-1600°C. In the off-axis case, the layer quality (surface morphology and defect density) does not change though accompanied with Ge droplets accumulation at the surface. The Ge incorporation level was found to increase with temperature in the 10171018cm-3ranges. It was observed that adding GeH4leads to the increase of the n type doping level by a factor from 2 to 5 depending on the C/Si ratio. In the on-axis case, GeH4was only added to the gas phase before starting the SiC growth. It was found that there is a conditions window (temperature and GeH4flux) for which 3C-SiC twin free layers can be grown. Adding this foreign element before SiC growth clearly modifies SiC nucleation on on-axis substrate.

Understanding of the Growth Mechanism Leading to Twin Boundary Elimination during 3C-SiC Heteroepitaxy on α-SiC Substrate by CVD

“…This delay in 3C-SiC growth is attributed to the presence of Ge atoms on the surface. Indeed, as showed in ref [6], a high flux of GeH 4 during surface preparation promotes the stabilization of 4H homoepitaxy against 3C nucleation despite the low off-axis of the seeds. In order to interpret this result, a different scenarii can be proposed.…”

“…It has been tuned either by specific surface preparation of the SiC substrates [5] or by changing the deposition chemistry [2]. In our previous work, we reported on the beneficial effect of Ge pre-deposition for 3C-SiC nucleation and growth of twin free layers on low off-axis α-SiC substrates using CVD [6]. The present work aims at understanding the processes which stand behind this result through a study of the early stages of nucleation and growth.…”

Microstructural Characterization of 3C-SiC Layers, Grown Epitaxially on 4H-SiC Substrates by CVD

“…before adding SiH 4 and C 3 H 8 to start the CVD growth. The growth temperature is 1500 ° C. For more information on growth related studies with similar experimental conditions see reference [8,9].…”

“…But experimentally, the growth of high quality 3C-SiC (111) layers on α-SiC (0001) substrates is very difficult due to the quasi-systematic formation of a high density of twin boundaries (TB). Recently, a chemical vapour deposition (CVD) technique using a GeH 4 gas flow as a surface pre-treatment prior to the growth, has demonstrated the possibility to drastically reduce twin boundaries in 3C-SiC grown on 4H SiC substrate with an optimal GeH 4 flux [8,9]. In our previous report [10], we described a high competition between homo and heteroepitaxy and a formation of a complex twinning system when using a low GeH 4 flux of 0.02 sccm.…”

Preliminary Study on the Effect of Micrometric Ge-Droplets on the Characteristics of Ni/4H-SiC Schottky Contacts

“…Considering Ge-incorporation, in the last decade ion implantation induced SiC:Ge heterostructures [4] or growth of heavily Ge-doped layers for Ohmic contacts [5] have been reported. More recently, Ge-incorporation in 4H-SiC, achieved by the addition of GeH 4 during epitaxial growth, has been demonstrated [6] and the effect of Ge on the intentional n-type doping has been discussed [7]. Preliminary studies on these Gedoped 4H-SiC epilayers showed an increased conductivity [8] and almost ideal characteristics of Ni 2 Si Schottky contacts [9].…”