Gas source molecular beam epitaxy (GSMBE) is a versatile tool For epitaxial growth of Si and SiGe from hydride precursors offering control on the atomic level, low thermal budget, a host of in-situ surface diagnostic tools, and possibility of selective epitaxial growth (SEG). However, the technique suffers from a much smaller growth rate in comparison to chemical vapour deposition (CVD) or solid source MBE. Where a process requires non-selective epitaxial growth (NSEG), the large contrast between growth rates over silicon and SiO2 surfaces make it impractical. These deficiencies are overcome by addition of a pum pi ng system with managed throughput thus allowing the system to be operated in a new ultra low pressure CVD (ULPCVD) mode as well as the conventional GSMBE mode. The modified system call achieve growth rate in excess of 0.5 mum/h and Cull NSEG in the ULPCVD mode while maintaining all the capability and advantages of GSMBE mode. The materials and structures an characterised and are shown to be better in many respects compared with those grown under conventional GSMBE.