Well depth fluctuation of Si_1-xGe_x/Si quantum well structures studied by conductance–voltage technique

A conductance method is proposed to study the interfacial band offset and the well depth fluctuation of SiGe/Si quantum well structures. Based on an equivalent circuit model, the frequency-dependent and temperature-dependent conductance–voltage (G–V) characteristics of quantum well structures are analyzed. It is revealed that corresponding to each well a conductance peak will appear in the G–V curve and meanwhile a capacitance step will appear in the capacitance–voltage curve. By this conductance method the position of the Fermi level as functions of applied bias voltage and temperature can be obtained in a wide voltage range. The conductance method is found to be an effective method to measure not only the band offset of single quantum well but also the well depth fluctuation of multiple quantum wells. © 1998 American Institute of Physics.