TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The buffer region has germanium layer having threading dislocation density of less than 105/cm2 and thickness of more than 5 mu m, preferably 0.1-1 mu m, and comprises active block(s) such as primary active block comprising germanium layer formed directly on silicon substrate. The buffer region further comprises secondary active block comprising germanium-silicon-tin (Ge1-x-ySixSny, where x is 0.07-0.42, y is 0.01-0.2 and x:y is 3:1-5:1) layer which is lattice matched or pseudomorphically strained to the primary active block. The germanium-silicon-tin layer has bandgap of 0.8-1.4 eV, preferably 0.9-1.35 eV, and comprises alloy containing germanium-silicon-tin (Ge1-x(Si(~b)Sn1-(~b)x), where ( beta ) is 0.79 and x is more than 0 to less than 1). The secondary active block comprises p-doped, n-doped or intrinsic silicon-germanium-tin (Si0.075Ge0.905Sn0.02, Si0.08Ge0.9Sn0.02, Si0.19Ge 0.76Sn0.05, Si0.2Ge0.745Sn0.055, Si0.23Ge0.71Sn0.06, Si0.26Ge0.67Sn0.07, Si0.3Ge0.6Sn0.1, Si0.31Ge0.6Sn0.09, Si0.32Ge0.64Sn0.04, Si0.41Ge0.48Sn0.1l or Si0.27Ge0.56Sn0.17), or its mixtures, each lattice matched or pseudomorphically strained to germanium layer. The germanium-tin layer comprises germanium-tin alloy (Ge1-xSnx, where x is 0.01-0.2). The primary active block comprising p-n junction or p-i-n junction contains germanium-silicon-tin alloy (Ge1-x-ySixSny, where x is 0.19-0.37 and y is 0.02-0.12, preferably y is 0.05-0.09) preferably contains silicon-germanium-tin (Si0.075Ge0.905Sn0.02, Si0.08Ge0.9Sn0.02, Si0.19Ge 0.76Sn0.05, Si0.2Ge0.745Sn0.055, Si0.23Ge0.71Sn0.06, Si0.26Ge0.67Sn0.07, Si0.3Ge0.6Sn0.1, Si0.31Ge0.6Sn0.09, Si0.32Ge0.64Sn0.04, Si0.41Ge0.48Sn0.1l or Si0.27Ge0.56Sn0.17). The primary active block has bandgap of 0.8-1.4 eV. The each III-V active block has p-n or p-i-n junction and comprises binary, tertiary, quaternary or higher indium-gallium-aluminum arsenic-antimony-phosphorus semiconductor. The primary III-V active block formed on the buffer region comprises p-doped, n-doped or intrinsic aluminum-gallium-arsenide indium phosphide (AlzGa1-zAs)a(InP)1-a or its mixture. The secondary III-V active block comprises p-doped, n-doped, or intrinsic aluminum-indium phosphide gallium phosphide (AljIn1-jP)b(GaP)1-b or its mixture formed on the primary III-V active block. The semiconductor structure further comprises a tunnel junction formed between each of several III-V active blocks. The silicon substrate has diameter of more than 3 inches. The buffer region and/or several III-V active blocks are formed by source molecular beam epitaxy, chemical vapor deposition, plasma enhanced chemical vapor deposition, laser assisted chemical vapor deposition or atomic layer deposition. The layers of buffer region are prepared by chemical vapor deposition using digermane, silylgermane, trisilane and/or stannane. The silicon-tin concentration in each layer is tuned by reaction of trisilane and stannane as the sources of silicon and tin respectively. The buffer region comprises germanium layer formed by contacting silicon substrate with chemical vapor comprising an admixture of organic germanium compound ((H3Ge)2CH2 and/or H3GeCH3) and digermane (Ge2H6), and germanium-tin layer formed by contacting silicon substrate with chemical vapor comprising digermane and tin compound-deuterium (SnD4) or hydrogen. The germanium-silicon-tin layer is formed by contacting germanium-tin layer with chemical vapor comprising germylsilane or silicon-based compound (SiH3SiH2SiH3), and tin compound-deuterium (SnD4).