P. P. Maltsev

Investigation of the optical properties of GaAs with δ-Si doping grown by molecular-beam epitaxy at low temperatures

Molecular-beam epitaxy is used for the preparation of structures based on “low-temperature” grown GaAs with introduced d-Si doping. Specific features in the photon-energy range of 1.28–1.48 eV are observed in the photoluminescence spectrum after structures annealing at temperatures of 520 and 580°C; these features are related to the formation of point defects and their complexes. The “pump–probe” light transmission measurements reveal that the characteristic lifetimes of nonequilibrium carriers in the fabricated structures amount to Tc ≈ 1.2–1.5 ps.

MHEMT with a power-gain cut-off frequency of fmax = 0.63 THz on the basis of a In0.42Al0.58As/In0.42Ga0.58As/In0.42Al0.58As/GaAs nanoheterostructure

The method of molecular-beam epitaxy is used to grow a In0.42Al0.58As/In0.42Ga0.58As/In0.42Al0.58As nanoheterostructure with a step-graded metamorphic buffer on a GaAs substrate. The root-mean-square value of the surface roughness is 3.1 nm. A MHEMT (metamorphic high-electron-mobility transistor) with a zigzag-like gate of a length of 46 nm is fabricated on the basis of this nanoheterostructure; for this MHEMT, the cutoff frequencies for the current and power gain are fT = 0.13 THz and fmax = 0.63 THz, respectively.

Metamorphic nanoheterostructures for millimeter-wave electronics

Electrical parameters and root-mean-square surface roughness of the metamorphic InAlAs/InGaAs/InAlAs nanoheterostructures with different indium contents (0.30–0.55) have been investigated. Field-effect transistors with the gate length Lg = 140−265 nm fabricated on the basis of metamorphic nanoheterostructures with an indium content of ~40% in the channel exhibit the current and power gain cutoff frequency fC = 147 GHz and fmax = 266 GHz, respectively.

Electrical and optical properties of near-surface AlGaAs/InGaAs/AlGaAs quantum wells with different quantum-well depths

A series of AlGaAs/InGaAs/AlGaAs quantum-well heterostructures with different quantum-well depths and approximately the same concentrations of two-dimensional electrons is grown by molecular-beam epitaxy. The built-in electric field in the grown samples is determined from the photoreflectance data and, on this basis, the energy-band structure in the quantum-well region is calculated. It is found that the highest mobility μe of two-dimensional electrons is attained in the sample with a barrier-layer thickness of Lb = 11 nm. Measurements of the photoluminescence spectra and the band-structure calculations demonstrate that, as the quantum well becomes closer to the surface, the doping profile broadens due to diffusion and segregation processes. The nonmonotonic dependence of μe on the distance between the surface and the quantum well is explained.

Promising materials for an electronic component base used to create terahertz frequency range (0.5–5.0 THz) generators and detectors

A THz transistor based on a metamorphic nanoheterostructure with generation frequency fmax = 0.63 THz and a zigzag-shaped gate Lg = 46 nm long is developed. A series of low-temperature GaAs structures are produced, and photoconductive antennas with generation frequencies above 1.5–2 THz are developed on their basis.

Experimental determination of the electron effective masses and mobilities in each dimensionally-quantized subband in an InxGa1 − xAs quantum well with InAs inserts

HEMT structures with In0.53Ga0.47As quantum well are synthesized using molecular-beam epitaxy on InP substrates. The structures are double-side Si δ-doped so that two dimensionally-quantized subbands are occupied. The effect of the central InAs nanoinsert in the quantum well on the electron effective masses m* and mobilities in each subband is studied. For experimental determination of m*, the quantum μq and transport μt mobilities of the two-dimensional electron gas in each dimensionally-quantized subband, the Shubnikov-de Haas effect is measured at two temperatures of 4.2 and 8.4 K. The electron effective masses are determined by the temperature dependence of the oscillation amplitudes, separating the oscillations of each dimensionally-quantized subband. The Fourier spectra of oscillations are used to determine the electron mobilities μq and μt in each dimensionally-quantized subband. It is shown that m* decreases as the InAs-nanoinsert thickness d in the In0.53Ga0.47As quantum well and electron mobilities increase. The maximum electron mobility is observed at the insert thickness d = 3.4 nm.

X-Ray diffractometry of metamorphic nanoheterostructures

Elastic strains in active regions of metamorphic transistor nanoheterostructures In0.7Al0.3As/In0.7Ga0.3As/In0.7Al0.3As on GaAs substrates with a metamorphic buffer (MB) having different complex designs have been determined by X-ray diffractometry. The objects of study are linear-graded MBs with different thicknesses, including those with internal strain-balanced superlattices or internal inverse steps, and a step-graded MB. All MBs are completed with an inverse step. The experimental results are compared with model predictions for hypothetical linear-graded MBs with the same average compositional gradients as for the samples under study.

Specific features of the photoluminescence of HEMT nanoheterostructures containing a composite InAlAs/InGaAs/InAs/InGaAs/InAlAs quantum well

The specific features of the photoluminescence and the electrical properties of doped nanoheterostructures containing a composite InAlAs/InGaAs/InAlAs quantum well with a thin InAs insert in the middle are studied. The insert thickness is varied in the range from 1.7 to 3.0 nm. It is established that the position of the peaks in the photoluminescence spectra in the photon energy range 0.6–0.8 eV correlates with the InAs insert thickness. Simulation of the band structure shows that the experimentally observed variation in the energy of optical transitions is associated with lowering of the energy of electron and hole states in the quantum well with increasing insert thickness. In the photon energy range 1.24–1.38 eV, optical transitions in the region of the InAlAs buffer-InP substrate interface are observed. The signal photon energy and intensity depend on the features of the formation of this heterointerface and on the conditions of substrate annealing. It is conceived that this is due to the formation of a transition region between the InAlAs buffer and the substrate.

Erratum to: “Structural and electrical properties of InAlAs/InGaAs/InAlAs HEMT heterostructures on InP substrates with InAs inserts in quantum well”

A complex study of the influence of nanoscale InAs inserts with thicknesses from 1.7 to 3.0 nm introduced into In0.53Ga0.47As quantum wells (QWs) on the structural and electrical properties of In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As heterostructures with one-sided δ-Si-doping has been performed. The structural quality of a combined QW was investigated by transmission electron microscopy. A correlation between the electron mobility in QW with the thickness of InAs insert and the technology of its fabrication is established. Specific features of the InP(substrate)/InAlAs(buffer) interface are investigated by transmission electron microscopy and photoluminescence spectroscopy. A relationship between the energy positions of the peak in the photoluminescence spectra in the range of photon energies 1.24 eV < ħω < 1.38 eV, which is due to the electronic transitions at the InP/InAlAs interface, and the structural features revealed in the interface region is established. It is found that an additional QW is unintentionally formed at the InP/InAlAs interface; the parameters of this QW depend on the heterostructure growth technology.

Photoluminescence of heterostructures containing an InxGa1–xAs quantum well with a high in content at different excitation powers

The results of studies of the photoluminescence spectra of heterostructures containing an InxGa1–xAs quantum well with a high In content x at different laser-radiation powers are reported. It is found that, as the radiation power density is increased, the luminescence spectrum of In0.70Al0.30As/In0.76Ga0.24As quantum-well heterostructures exhibits a decrease in the half-width and a shift of the peak to higher energies. It is shown that, for Al0.27Ga0.73As/In0.20Ga0.80As quantum-well heterostructures, no shift of the peak and no change in the shape of the spectrum is observed. It is established that the integrated photoluminescence intensity is related to the laser-radiation power density by a power law with the exponent α ≈ 1.3 for heterostructures with x ≈ 0.76, suggesting the predominantly excitonic character of the radiative recombination of charge carriers.