Doping-concentration dependence of a boron-doped p-type Ge layer grown on a Si (100) substrates by using RTCVD

Boron-doped p-type Ge layers were grown on n-type Si (100) wafers at various boron doping concentrations by using Rapid Thermal Chemical Vapor Deposition. The root-mean-square was surface roughness of p-type Ge layer increase from 0.708 nm to 19.980 nm as the doping concentrations increase from 3 × 10¹⁶ cm^-3 to 4 × 10²² cm^-3. From High Resolution X-ray diffraction, the in-plane lattice constants and tensile strains of the p-type Ge layer were evaluated as function of boron doping concentration the Raman shift of the for each location indicate a tensile strain from the p-type Ge layer. The tensile strain of the p-type Ge layer decreases from 0.071% to 0.032% as the boron doping concentrations increases from 3 × 10¹⁶ cm^-3 to 4 × 10²² cm^-3. Moreover, the photocurrent peak energies increased. The temperature dependence of the direct band-gap energy, E, of the p-type Ge layer could be described by using Varshnis empirical expression: E_Γ(T) = 0.86 - 5.82 × 10^-4 T₂/(T + 296).