Growth and doping of silicon carbide with germanium: a review

Abstract

This paper review the research works made so far in associating Ge isoelectronic element to SiC crystals, either by incorporating it inside SiC matrix or for assisting SiC epitaxial growth. The incorporation mechanism and level of incorporation of Ge in SiC during crystal growth with different techniques (sublimation, chemical vapor deposition, vapor-liquid-solid) are compared and discussed. Ge doping level as high as 2-3x10 20 at.cm -3 can be reached without affecting SiC crystalline quality but generating some strain. Higher Ge incorporation levels up to few at% can be reached using farer-toequilibrium conditions such as ion implantation or molecular beam epitaxy. The former allows retaining 4H-SiC polytype while the latter leads exclusively to defective 3C-SiC polytype. Adding Ge to SiC crystal growth was also used for promoting 3C-SiC heteroepitaxy on Si and on -SiC substrates, the latter case being more successful. The reported modifications and improvements of SiC crystalline and electronic properties by the incorporation of Ge element are discussed in order to draw or clearer picture of SiC:Ge material. Based on such discussion, some short-and long-term perspectives are proposed 1-IntroductionThe development of any semiconductor based technology requires mastering and understanding a high number of fabrication steps which can be very complex. On material aspect, crystalline quality and purity are essential. The former allows reaching the predicted properties of the material while the latter allows working on the intentional doping type and level of the semiconductor. The n and p type doping elements are usually well identified for each semiconductor and their incorporations using different elaboration techniques are widely documented. The incorporation of metallic impurities is also commonly investigated for improving the semiconductor properties such as increasing resistivity (Fe in GaN [1], V in 4H-SiC [2]), tuning optical emission (Er in GaN [3] or Si [4]) or providing magnetic properties (Mn in GaAs [5] or Ge [6]). Isoelectronic (also named isovalent) doping is similarly frequent in the case of binary (III-V or II-VI) semiconductor compounds due to the usual important miscibility between elements of the same column and/or valence. It can lead to bandgap tuning [7,8], obtaining of new properties [9,10] or crystalline improvement [11,12].In the particular cases of column IVB semiconductors, the isoelectronic doping concerns only elements of the same column which reduces substantially the possibilities. Important solubility exists

Effect of TCS gas flow and pre-etching on homopitaxial growth of 4H-SiC

“…The internal bond energy of N 2 itself is high, and even at a high temperature of 1570 °C, the number of N atoms generated by decomposition is very limited. 21 Therefore, simply increasing the flow rate of N 2 does not correspondingly increase the number of doping atoms entering the substrate and thus the doping concentration. Additionally, due to the acceleration of the growth rate, the doping concentration will decrease accordingly.…”

“…The internal bond energy of N 2 itself is high, and even at a high temperature of 1570 °C, the number of N atoms generated by decomposition is very limited. 21 Therefore, simply increasing the ow rate of N 2 Fig. 1 Growth rate and thickness uniformity under different source gas flow rates.…”

A Study of High Resistivity Semi-Insulating 4H-SiC Epilayers Formed via the Implantation of Germanium and Vanadium

“…For 4H-SiC, the most common semi-insulating impurity is vanadium (V), which is often incorporated during substrate or epitaxial growth [4]. Recently, the introduction of germanium (Ge) has shown interest and yielded some potential benefits via epitaxy [5] or implantation [6] into SiC, with lower Z1/2 levels [7], higher mobility [8] and higher conductivity [9]. However, less is known about the combination of Ge with additional n-type compensation doping.…”