A new method of investigating the quantum channel surface

A new method of investigating the quantum channel surface was used to study the germanium quantum well in a SiGe/Ge/SiGe p-type heterostructure, with a hole concentration p(H) = 5.68 x 10(11) cm(-2) and mobility mu = 4.68 x 10(4) cm(2) V-1 s(-1) in magnetic fields up to 15 T and in the temperature range 50 mK-3 K using Shubnikov-de Haas (SdH) oscillations. The method is based on the deviation from theory describing the SdH-related conductivity oscillations. This deviation appears due to extra broadening of the Landau levels, which is attributed to the existence of an inhomogeneous distribution of the carrier concentration in the two-dimensional hole gas layer and, hence, a spread of energy. It is assumed that extra broadening is due to the natural variation of the well width equal to the interatomic distance. The effective hole mass (m* = 0.112m(0)) was found from the temperature dependence of the SdH oscillation amplitudes. The quantum scattering time, fluctuations of the carrier concentration and quantum well roughness were estimated from the magnetic field dependence of these oscillation amplitudes