Study of subband electronic structure of Si δ-doped GaAs using magnetotransport measurements in tilted magnetic fields

Abstract

Si δ-doped GaAs grown by metal organic vapor phase epitaxy (MOVPE) is characterized using magnetotransport measurements in tilted magnetic fields. Angular dependence of the longitudinal magnetoresistance (Rxx) vs the magnetic field (B) traces in tilted magnetic fields is used to examine the existence of a quasi-two-dimensional electron gas. The subband electron densities (ni) are obtained applying fast Fourier transform (FFT) analysis to the Rxx vs B trace and using mobility spectrum (MS) analysis of the magnetic field dependent Hall data. Our results show that (1) the subband electron densities remain roughly constant when the tilted magnetic field with an angle <30° measured from the Si δ-doped plane normal is ramped up to 13 T; (2) FFT analysis of the Rxx vs B trace and MS analysis of the magnetic field dependent Hall data both give the comparable results on subband electron densities of Si δ-doped GaAs with low δ-doping concentration, however, for Si δ-doped GaAs with very high δ-doping concentration, the occupation of the lowest subbands cannot be well resolved in the MS analysis; (3) the highest subband electron mobility reported to date of 45 282 cm2/s V is observed in Si δ-doped GaAs at 77 K in the dark; and (4) the subband electron densities of Si δ-doped GaAs grown by MOVPE at 700 °C are comparable to those grown by MBE at temperatures below 600 °C. A detailed study of magnetotransport properties of Si δ-doped GaAs in the parallel magnetic fields is then carried out to further confirm the subband electronic structures revealed by FFT and MS analysis. Our results are compared to theoretical calculation previously reported in literature. In addition, influence of different cap layer structures on subband electronic structures of Si δ-doped GaAs is observed and also discussed.

Classical magnetotransport in a parabolic quantum well with a strong intersubband scattering

“…From the fact that at V g > −0.25 V two subbands are occupied with mobilities around 10-20 m 2 V −1 s −1 one should expect a strong magnetoresistivity effect in a range of the magnetic field B ∼ 1/µ ∼ 0.1 T predicted by classical formulae [22] for multilayer conductivity. Such a picture was appropriate for delta-doped structures where the conductivity could be described as a sum of electron species with different mobilities [8,13]. However, as will be shown later, it did not work in the case of PQWs.…”

“…In both systems several subbands can be occupied easily with a substantial portion of the electron population in the higher subbands. Much effort of researchers has been concentrated on transport properties of DDLs [8][9][10][11][12][13][14][15][16], and recently the PQWs have been receiving growing attention as well [17][18][19].…”

Deep levels in GaAs due to Si δ doping

“…They can serve as a source of free carriers in modulation-doped field effect transistors 1,2 or power devices, 3 allow one to produce low-resistivity ohmic contacts 4,5 or to obtain high-field regions for studying and applying electro-optical effects, 6,7 for example. Moreover, because the ␦ doping produces a self-consistent potential well confining a two-dimensional ͑2D͒ electron system with a high degree of disorder, basic physical properties of the two-dimensional electron gas have been studied in ␦ layers mainly by magnetotransport and optical methods [8][9][10] with a special emphasis put on a detailed analysis of the influence of disorder on the transport and the localization in twodimensional systems. [11][12][13][14] An elementary characterization of the ␦ layers is often performed by a capacitance-voltage (C -V) measurement in structures where the ␦ layer is involved in a space charge region ͑SCR͒ of the Schottky barrier.…”

The orbit centre dependence of the energy levels in a single quantum well under external tilted magnetic and electric fields

“…Many experiments with tilted magnetic fields include mixing of degenerate Landau levels originating from different electronic subbands (induced by the magnetic field component parallel to the growth direction in cyclotron resonance experiments [1,2]), and the cos θ dependence of the amplitudes in Shubnikov-de Haas (SdH) oscillations in early experiments on modulation doped structures [3,4], and recently on Si δ-doped structures [5], where θ is the tilt parameter. In a parabolic potential well eigenenergies of two-dimensional electrons subjected to a tilted magnetic field have been solved analytically by Maan [6].…”