Solid phase epitaxy of amorphous Ge on Si in N2 atmosphere

Abstract

We demonstrate a straightforward and economical way to obtain smooth germanium layers of high quality on silicon. Thin amorphous germanium layers deposited by plasma enhanced chemical vapor deposition on Si(111) substrates are transformed into single crystalline and smooth layers by solid phase epitaxy in N2 atmosphere. The crystal orientation of the substrate has a clear influence on the crystal quality. This is most likely due to a different growth mode, namely, layer-by-layer for Si(111) and three-dimensional growth for Si(001). The amorphous germanium layer can roughen during annealing due to mobile atoms on the surface. This can be effectively suppressed by annealing in N2 ambient. Electrical measurements show high charge mobility.

New RP‐CVD grown ultra‐high performance selectively B‐doped pure‐Ge 20 nm QWs on (100)Si as basis material for post‐Si CMOS technology

“…An extremely high mobility of 1.34×10 6 cm 2 /Vs at p s = 2.9×10 11 cm -2 has been determined for the normal heterostructure at 500 mK. This result for holes in germanium is comparable with the highest reported electron mobility for a 2DEG stretched silicon channel of 1.6×10 6 cm 2 /Vs at a carrier sheet density of 1.5×10 11 cm -2 observed at 0.3 K [20]. The mobility for the inverted structure was found to be 0.51×10 6 apart from our normal structure.…”

Single crystalline SiGe layers on Si by solid phase epitaxy

“…A (111) substrate is used in the method described below as it enhances the crystal quality compared to that of a (100) crystal [14]. The reduced density of crystallization sites at the (111)-crystal/amorphous interface promotes planar growth while island formation is suppressed.…”

“…Previously, we have shown excellent electrical properties of P-doped and B-doped Ge layers on Si, using the SPE method [14]. After introducing P or B with phosphine (PH 3 ) or diborane (B 2 H 6 ) gas an electron (hole) concentration of 2:6 Â 10 18 cm À 3 (5:4 Â 10 18 cm À 3 ) with a mobility of 271 cm 2 /V s (149 cm 2 /V s) was measured.…”

“…Previously we have demonstrated the possibilities of solid phase epitaxy (SPE) of amorphous Ge and Ge 1 À x Sn x layers on Si [14,15]. In this work, we will demonstrate the possibilities of plasma enhanced chemical vapour deposition (PECVD) and SPE for the fabrication of single crystalline SiGe compounds.…”

Processing of germanium for integrated circuits

“…Yamamoto et al proposed a processing methodology to reduce the threading dislocation density in Ge layers grown on Si, namely reduced pressure CVD in combination with HCl etching [12]. Lieten et al used a solid phase epitaxy (SPE) process of amorphous Ge on (111) Si to form Ge on Si substrates [13]. The Ge was deposited by plasma enhanced chemical vapour deposition, and a thermal anneal produced crystallisation using the Si wafer as a template.…”