Dopant electrical activity of Si and Si1−xGex multilayer structures doped with δ-like boron spikes at different temperatures

Boron spikes within multilayer structures of Si and of Si1−xGex deposited by means of molecular-beam epitaxy (MBE) at different temperatures have been investigated by secondary-ion-mass spectrometry (SIMS), spreading resistance, and Hall-effect measurements. For a Ge amount of x=7% it is shown that segregation effects, electrical activity of B, steepness of B spikes, and solid solubility of B differ in Si and Si1−xGex at the same deposition temperatures. For Si1−xGex growth the surface segregation is significantly reduced in comparison to the growth of Si layers. Steeper B profiles can be obtained at same temperatures but the amount of electrically inactive B is higher. Calculations of the charge-carrier distributions near the spikes have been performed using classical and quantum mechanical approaches to find out reasons for deviations of the concentration profiles of B and of holes obtained from SIMS and from spreading resistance measurements, respectively.