Low-temperature magnetoresistance due to weak localization in lightly doped semiconductors

Specific features of the low‐temperature microwave magnetoresistance in nondegenerate p‐Ge

“…Another specific feature of these curves is that they exhibit two peaks of negative values of the MC derivative. In [1,2], these peaks were attributed to MC associated with light and heavy holes. It can be seen, however, in Fig.…”

“…We begin with an analysis of the existence of two minima in the field dependence of the MC derivative. Originally, it seemed that this effect is governed by the interference contribution to MC in weak fields, as it occurs in n-Ge [1,2]. However, these two minima are preserved up to rather high temperatures, at which no interference contribution can exist.…”

“…1 Introduction Previously, we have reported an observation of the negative magnetoresistance (MR) [positive magnetoconductance (MC)] in lightly doped (nondegenerate) Ge at low temperatures in the microwave frequency range (~10 GHz) [1,2]. This was done using the electron spin resonance (ESR) method, which records the derivative of the microwave absorption with respect to magnetic field, proportional, in samples with high resistance, to the derivative of MC, dP/dH ~ dσ/dH.…”

“…In this case, the change of sign by the derivative is due to specific physical features of the field dependence of MC and will be considered below. Figure 1 Field dependence of the microwave absorption, measured with the ac modulating magnetic field switched (1) on and (2) off at T = 14 K. Figure 2 shows field dependences of the MC derivative at different temperatures for the p-Ge sample with p ≈ 3×10 14 cm -3 early investigated in [1,2]. The curves are normalized in such a way that the minimum value of the derivative is unity at all temperatures.…”

Angular and temperature-related specific features of averaging of hole effective masses in p-Ge at low temperatures

“…We have shown previously [1][2][3] that the averaging of the hole effective mass in lightly doped p-Ge occurs during a time comparable with the energy scattering time, rather than with the momentum scattering time, as it has been believed so far [4]. Our conclusion was based on measurements of the dependence of the microwave energy absorption (frequency 10 10 Hz) on the magnetic field at low temperatures [magnetoabsorption (MA)].…”