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The thermal stability of a SiGe/Si quantum well grown by molecular-beam epitaxy is studied by using the admittance spectroscopy technique. The values of activation energies of hole emission from the subbands in the SiGe/Si quantum well are derived from the admittance spectra. After annealing the sample at different temperatures, the activation energy varies in different behaviors. There is no significant change of the activation energy after annealing at 700 °C for 40 min. At the annealing temperature of 900 °C, the decrease of the activation energy with annealing time could be attributed to the interdiffusion of Ge, Si atoms at the heterointerfaces and the strain relaxation effect. An unexpected phenomenon is observed at the annealing temperature of 800 °C, i.e., the activation energy increases with the annealing time. This extraordinary phenomenon is supposed to be caused by the change of the well potential shape due to the B out-diffusion from the well to the Si barrier.

The interfacial defects at the p‐Si epitaxial layer/p‐Si substrate interface have been studied by deep‐level transient spectroscopy (DLTS). By solving Poisson equation, the electron concentration at the defect level varied with external voltage is derived. The emission and capture of electrons at the defect level, which are not observable in conventional DLTS, can be detected simultaneously in a single temperature scan by properly choosing the experimental parameters. The experimental results show that the energy level of the interfacial defects is located at Ec−0.30 eV.

A single‐frequency admittance spectroscopy technique is presented to determine the band discontinuity of the Si/Si1−xGex/Si single quantum well. The accuracy of determining the activation energy for thermionic emission of holes over the Si barrier is improved as compared with the multiple‐frequency admittance spectroscopy measurement. To derive the band offset from the activation energy, the Fermi energy with respect to the band edge is calculated more exactly by solving the Poisson equation which accounts for the carrier transfer at the heterointerface. The accuracy of this technique is verified by the reconstruction of the temperature dependence of capacitance and conductance by the computer simulation.