A.P. Senichkin

Transport and optical properties of tin-delta-doped GaAs structures

The transport and optical properties of tin δ layers in GaAs are investigated as functions of the Sn concentration. The Shubnikov-de Haas and Hall effects are measured in the temperature range 0.4–12 K in magnetic fields up to 38 T. The band diagrams and quantum mobilities of electrons in the quantum-well subbands are calculated. Features associated with electronic transitions from quantum-well levels are found in the photoluminescence spectra of the structures. Oscillations of the resistance are observed in a magnetic field parallel to the δ layer and are attributed to features in the density of states at the Fermi level.

Quenching of persistent photoconductivity and decrease of electron concentration by high electric fields in GaAs delta-doped by Sn on vicinal substrate structures

Abstract This paper reports the measurements of high electric field transport and the persistent photoconductivity in delta-doped by Sn on vicinal and singular substrate GaAs structures. Transport properties of the hot electron gas were measured in the temperature range 4.2 K

Wavelength dependent negative and positive persistent photoconductivity in Sn δ-doped GaAs structures

The photoconductivity of GaAs structures δ-doped by Sn has been investigated for wavelengths λ = 650-1200 nm in the temperature interval T = 4.2-300 K. The electron densities and mobilities, before and after illumination, have been determined by magnetoresistance, Shubnikov-de Haas effect and Hall effect measurements, in high magnetic fields. For the heavily doped structures (Hall density nH>2×1013 cm-2) we observe under illumination by light with wavelengths larger than the bandgap wavelength of the host material (λ = 815 nm at T = 4.2 K) first positive (PPPC) and then negative (NPPC) persistent photoconductivity. The NPPC is attributed to the ionization of DX centres and PPPC is explained by the excitation of electrons from Cr impurity states in the substrate. For λ<815 nm, in addition, the excitation of electrons over the bandgap of GaAs contributes to the PPPC. For the lightly doped structures (nH≤2×1013 cm-2) the photoconductivity effect is always positive.

Negative persistent photoconductivity in GaAs (δ-Sn) structures

The effect of illumination with various wavelengths λ (770 nm<λ<1120 nm) on the conductivity of GaAs structures with tin δ-doping of the vicinal faces was investigated in the temperature range 4.2–300 K. Negative persistent photoconductivity was found in strongly doped samples. It was shown on the basis of the results of investigations of the Hall and Shubnikov-de Haas effects that the negative photoconductivity is due to a large decrease in the electron mobility with increasing electron density. The decrease of electron mobility is explained by ionization of DX centers, which destroys the spatial correlation in the distribution of positively charged donors and negatively charged DX centers.

Conducting wires embedded in an i -GaAs matrix for electronic applications

Abstract A method of fabricating quasi-1D conducting wires of tin embedded in an i -GaAs matrix has been developed. The method involves forming a system of steps on vicinal surface of the GaAs(Cr) substrate misoriented 0.3° or 1° from the (001) plane forward to the (110) basal plane and decorating the ends of these steps with Sn through molecular-beam epitaxy. Transport properties of structures were measured in the temperature range 4.2–300 K at high electric fields up to E= 10 4 V/cm using a pulse technique.

Low-temperature subband 2D electron mobilities in heavy delta- and modulation doped GaAs/GaAlAs heterostructures

We synthesised high-2D electron-density GaGs/GaAlAs heterostructures with different distance Lσ of Si delta-layer in GaAs from the heterojunction and uniform doped GaAlAs. The quantum Hall effect and Shubnikov-de Haas effect were measured for temperatures down to 0.4 K in magnetic fields up to 40 T. The enhanced 2D electron concentration achieved was 1.1*1013 cm−2 in six filled subbands. The Hall mobility depends on Lσ and has maximum for Lσ=600÷750Å. From the amplitudes of the SdH oscillations and Fourier transforms the subband mobilities and electron concentration in each subband have been extracted. According to calculations intersubband electron scattering appears to be important and reduces mobilities in subbands.

Low temperature negative magnetoresistance in the δ-doped by Sn and Si on vicinal and singular substrates GaAs structures

The anisotropy of conductivity and negative longitudinal and perpendicular magnetoresistance in GaAs deltadoped by Sn and Si on vicinal and singular surface structures was investigated in the temperature range 0,4K<T<100 K in magnetic fields B<8T. On a GaAs(Cr) substrate inclined at a small angle θ=0.3o from (001) plane to (110) plane with help of MBE GaAs(δ-Sn) or GaAs(δ-Si) structures were synthesised. The anisotropy of conductivity and NM is higher for GaAs(δ-Sn) structures on vicinal substrate. In parallel magnetic field one of the reason of the negative magnetoresistance is the 2D scattering. Making use the theory of the NM the parameters of 2D electrons were determined.