S. S. Khludkov

Influence of temperature on the mechanism of carrier injection in light-emitting diodes based on InGaN/GaN multiple quantum wells

The experimental current-voltage characteristics and dependences of the external quantum yield on the current density of light-emitting diodes based on InGaN/GaN multiple quantum wells for the wide temperature range T = 10–400 K are presented. It is shown that, at low-temperatures T < 100 K, the injection of holes into the quantum wells occurs from localized acceptor states. The low-temperature injection of electrons into p-GaN occurs due to quasi-ballistic transport in the region of multiple quantum wells. An increase in temperature leads to an increase in the current which is governed by thermally activated hole and electron injection from the allowed bands of GaN.

Decomposition of a supersaturated solid solution of Fe in GaAs

The decomposition of a solid solution of iron in gallium arsenide at 900°C has been studied by magnetic force microscopy and transmission electron microscopy. The results demonstrate that annealing of Fe-doped GaAs for 3 h leads to the formation of disk-shaped ferromagnetic inclusions 50–500 nm in diameter and 1.5–50 nm in thickness. The average inclusion concentration is 1011 cm−3. The estimated decomposition time of the solid solution at 900°C is within 1 h.

A study of the process of decomposition of supersaturated GaAs:Fe solid solution by scanning probe microscopy

Using an atomic-force microscope, the decomposition of the supersaturated solid solution of iron-doped GaAs (GaAs:Fe) is studied. GaAs:Fe samples were obtained in the course of high-temperature diffusion of Fe into GaAs and subsequent annealing at a temperature by 200°C below the doping temperature. The measurements are performed for transverse cleavages along the cleavage planes of the GaAs:Fe wafers. It is shown that, during annealing of the GaAs:Fe samples, the supersaturated alloy decomposes with the formation of particles of the second phase from ∼50 nm to ∼1 μm in size. The particles of the second phase possess ferromagnetic properties at room temperature.

Switching avalanche S-diodes based on GaAs multilayer structures

Results of studying volt-ampere characteristics of switching avalanche S-diodes are presented. It is shown that, for S-diodes based on structures obtained by diffusing Cr into GaAs, a larger part of the applied reverse-biased voltage drops across a high-resistance π-region but not across the space-charge region. In this case, the sharp increase of the current is caused by the electron injection from the forward-biased contact to the π-layer. In this respect, a new GaAs-based structure doped with Cr and Fe (GaAs:Cr, Fe) is studied. It is shown that, in S-diodes based on (GaAs:Cr, Fe)-structures, the current increase under a reverse bias is caused by avalanche processes in the space-charge area. This leads to producing a negative differential resistance section with subnanosecond switching from the closed to open state. The switching voltages of S-diodes on GaAs:Cr, Fe structures vary from 350 to 650 V, and the switching times do not exceed 0.5 ns.

Chromium diffusion in GaAs in an open system

We have studied chromium diffusion from a surface layer produced by thermal evaporation into n-type GaAs in a flowing inert-reducing atmosphere. The temperature dependences of the Cr diffusivity and solubility in GaAs are well represented by Arrhenius equations with D0 = 1.7 × 10−2 cm2/s and QD = 1.43 eV for the diffusivity and CCr0 = 8.9 × 1021 cm−3 and QCr = 1.22 eV for the solubility.

GALLIUM ARSENIDE STRUCTURES WITH DEEP CENTERS AND IONIZED RADIATION DETECTORS BASED ON THEM

Results of experimental studies of the effect of electromagnetic radiation over a broad spectral range and high-energy charged particles on gallium arsenide structures with deep centers are presented. It is shown that it is possible to create highly sensitive radiation-stable detectors for different forms of radiation on the basis of the structures studied.

Prospects for Application of Gallium Arsenide Doped with Transition Metals as a Material for Spintronics

This chapter is a review of the literature dealing with the production and properties of ferromagnetic gallium arsenide and the possibility of using it in spintronics. A study of ferromagnetic GaAs has been under way for two decades, and this material and the structures on its basis remain of great interest nowadays. In the review, the most attention is paid to the GaMnAs and GaFeAs materials, as well as ferromagnetic metal/GaAs structures. By the present day, the GaMnAs is one of the most promising spintronics materials. Despite the great number of studies devoted to the production and investigation of this compound, there exist urgent problems of raising the operating temperature of the structures based on GaMnAs increasing, for this purpose, the Mn content in the structures. The low solubility of Mn in gallium arsenide prevents from increasing the Curie temperature. Doping above this limit results in increasing the Mn concentration in the interstice and the development of individual phases manifesting both ferromagnetic and antiferromagnetic properties. Unlike GaMnAs, in the doping of GaAs with iron, a considerable contribution of the d-orbitals encourages aggregation of the Fe cautions and the formation of inclusions of the condensed magnetic semiconductor. The second-phase inclusions and Fe-based microclusters were observed in GaAs grown by different techniques. The paper discusses various effects for these materials: spin injection, giant magneto-optical effect, shift of the magnetic domain walls, interlayer exchange coupling, strong magnetic anisotropy, etc. The prospects have been shown for application of GaAs doped with transition metals in spintronics. A number of devices have been made, e.g., field-effect transistors and light-emitting diodes, a light-driven microactuator, magneto-optical materials, and magnetic field sensors.

Switching delay of avalanche S-diodes in circuit with optical drive

The results of study of avalanche S-diodes in circuit with pulse optical drive are presented. Experimental dependences of delay time of S-diodes switch on laser energy with wave-length 0.78 mkm are presented. It is shown that switching delay of avalanche S-diodes caused by recharging of deep traps in space charge region

A switching delay of avalanche S-diodes in optical-drive circuits

Results of studying avalanche S-diodes in a circuit with pulse optical drives are presented. The experimental delay time dependences of the S-diode switching from disabled to enabled states on the energy of the laser emission with a 0.78-μm wavelength are given. It is shown that the avalanche S-diode switching delay is caused by the deep-seated trap recharging process in the space-charge region.

Transformation of current-voltage characteristics of GaAs π-ν-n-structures under modification of π-layer resistance

Results of investigation of forward and reverse current-voltage characteristics (CVC) of diodes based on GaAs doped by Cr (GaAs:Cr) and doped by Cr, Fe simultaneously (GaAs:Cr,Fe) are stated. It is shown that reduction of base resistance of diodes based on compensated material lead to transformation of static CVC and to appearance of negative differential resistance (NDR) region on reverse CVC.