Magnetotransport study of the intersubband scattering in an Si -doped GaAs

Abstract

The magneto-transport of an FET with a channel of an Si δ-doped GaAs layer is studied at 4.2 K to reveal the transport properties in the subband structure. The Shubnikov-de Haas effect is analysed as a function of the gate bias voltage to estimate the variation of the electron density as well as the mobility in each subband. It is found that the carrier density decreases linearly as a function of the gate voltage. The electron mobility in a given subband shows however an anomalous nonlinear decrease, which is attributed to intersubband scattering.

The temperature dependence and scaling of the negative magneto-resistance in Si atomic-layer-doped GaAs

“…This shows that the deviation from the unified function observed in figure 1(b) occurs when the number of subbands participating in the transport is changed from two to one. It was shown that the electron mobility in the ground subband is much lower than that in the first excited states [15]. Thus the present result suggests that the magnitude of the NMR is determined by the number of subbands or the mobility of electrons participating in the transport.…”

“…In this particular sample the transport at zero electric field is due to parallel conduction with two subbands. Previous results [15] showed that the mobility in the lowest ground subband is as low as several hundreds of cm 2 V −1 s −1 , while those in higher excited subbands are one order of magnitude higher. The rapid increase of the electron mobility at high fields (or at high electron temperatures) suggests that the third subband participates the electron transport.…”

“…C-V and Hall measurements suggest that the autocompensation is negligible at (1.7 ∼ 5.0) × 10 12 cm −2 and the carrier saturation occurs at (10 ∼ 40) × 10 12 cm −2 [14]. In an as-grown sample, a few subbands are expected to be formed in the δ-doped layer [15].…”

“…By analysing the positive magneto-resistance component shown in equation ( 1), the mobility of electrons is estimated. It was found that the mobility is increased on application of the electric field, which is characteristic of ionized impurity scattering (see figure 8 of [15] or figure 9 below). In this particular sample, at fields studied the magnitude was 400 ∼ 800 cm 2 V −1 s −1 .…”

“…In order to estimate the width of the channels, the cyclotron radius of electrons at the saturation magnetic field B M is estimated at 4.2 K. If those electrons exhibiting the NMR are in the second subband, the classical cyclotron radius is given by r cyc = (2E F m * ) 0.5 /eB M , where E F is the Fermi energy which was derived from the SdH measurement [15]. B M was determined as the field where the extrapolation of the linear increase of the NMR gives the saturation value α M .…”