A. A. Vilisov

The effect of current crowding on the heat and light pattern in high-power AlGaAs light emitting diodes

The results of the light and temperature micromapping in AlGaAs light emitting diodes grown by liquid phase epitaxy as double heterostructures and emitting at λ∼0.87 μm are presented. At a driving current well above the safe operating limit (>300 mA), the nonuniform light pattern and local self-heating (with temperature gradient of about 950 °C/cm) followed by catastrophic degradation of a device were detected with the charge coupled device and infrared microscopes operating in a pulsed mode. These were shown to result from the current crowding effect in the active and contact areas of a device. Good agreement between the theory and experiment was found.

Research on Performance of Red Vertical AlGaInP/GaAs Light-Emitting Diodes Influenced by Current Crowding

The authors show that the performance of red vertical AlGaInP/GaAs light-emitting diodes is compromised by the current crowding (CC) effect in the moderate-current (space charge region dominates in the device performance) and high-current (series resistance dominates in the equivalent circuit of a device) domains. Depending on the contact pattern, a remarkable part of the performance degradation comes as a result of the electrical power lost on the series resistance (~17%). CC affects the ideality factor and causes the current spreading length to decrease from 425 at low currents to 75 at a current of 250 mA.

Electron bombardment effect on the reverse I–V characteristics and tensosensibility of p+-nGaAs diodes

Abstract The effect of ≈2 MeV electron bombardment on the reverse characteristics and tensoelectric properties in p+-nGaAs diodes is investigated. The reverse breakdown voltage showed a weak increase due to irradiation and an anomalous temperature dependence in the range 77–300 K. The I–V characteristics in electron-irradiated diodes revealed a high pressure sensitivity (tensosensibility) to the external hydrostatic pressure (up to 6 · 108 Pa). The peculiarities in the reverse I–V characteristics of diodes investigated point to the presence of a radiation-induced deep trap (acceptor-type level at about E0 − 0.3 + 0.4 eV), which is attached to the Γ15V-maximum of the valence band.

Nanosecond infrared radiators for short-range location systems

This paper presents the results obtained from the research of semiconductor radiators within the nanosecond range of radiated pulse time. The prospects for construction of pulsed optoelectronic devices are demonstrated.

Specialized LED for medical instrument making

The authors have developed a powerful radiating diode AL148A for radiation therapy in the 630-950 nm wavelength range.

Photoinduced improvement of the properties of light-emitting diodes

Results from studies of the effect of the action of optical radiation on the characteristics of light-emitting diodes (LEDs) produced using the binary heterostructure GaxAl1−xAs (λ=0.88 μm) are presented. High sensitivity of the LED to the following parameters of the optical radiation is shown: flux density, quantum energy, and exposure dose. The action of optical radiation in the form of a band with a maximum at 255 nm on the LED heterostructures lowers the leakage current into the bulk, decreases the loss identified as surface leakage current by about an order of magnitude, increases the radiated power by 50–100% in the current region up to 10−3 A, and increases the overall light output of the diodes.

Doping of solid solutions in liquid epitaxy. III. Tellurium in AlxGa1−xSb

A calculation is made of the dependences of the coefficient of the tellurium distribution KTe and the electron concentration n in AlxGa1−xSb on the composition of the solid solution and the growth temperature. It is shown that KTe must decrease with increasing x. The dependence of KTe on the temperature is also determined by x. Experimental results were obtained on AlxGa1−x Sb (0 ⩽ x ⩽ 0.74) films grown by liquid epitaxy. The electron concentration in the films was measured through the thermoelectric power and the capacitance-voltage characteristics of Schottky barriers. Satisfactory agreement with the results of the calculation was obtained.

Surface-barrier structures on AlxGa1−xSb. II. Band gap dependence of barrier height

The short-circuit photocurrent is used to find the forbidden gap width Eg and barrier height ΦB of Pd-n-AlxGa1−xSb (0.1 ⩽s x ⩽ 0.7) surface-barrier structure fabricated electrochemically. The barrier height was also determined from the capacitive voltage cutoff and the current-voltage characteristics. For metal-n-AlxGa1−xSb contacts the linear approximation to ΦB(Eg) is given by ΦB = 0.64Eg + 0.16 eV. In some samples the photoresponse spectrum has a hump, indicating the effects of deep levels.

Surface-barrier structures on AlxGa1−xSb. I. Preparation and physical model of the contact

The optimal conditions for preparing the surface and electrochemically depositing the metal have been determined for surface-barrier junctions of palladium on n-type gallium aluminum antimonide. The temperature and composition dependences of the voltage-current and voltage-capacitance characteristics of the junctions have been measured. When combined with the frequency dependence of the capacitance, these data show that, depending on the condition during formation, nearly ideal Schottky barriers are formed (i.e., a metal-intermediate layer-semiconductor system). The mechanism for current flow depends on the structure of the contact and the solid-solution composition. Anomalous barrier behavior at low temperatures is due to specific properties of the solid solution.

Effect of hydrostatic pressure on characteristics of GaAs-Ge1−x(GaAs)x heterojunctions

The conditions of obtention of nGaAs-pGe1−x(GaAs)x alloy heterojunctions and the behavior of the electrical and photoelectric characteristics of these structures under hydrostatic compression were investigated. It is shown that the mechanism of current transport in this structure is of the tunneling-recombination type. The pressure coefficients of the forbidden gap width in the solid solution, the effective electron mass in gallium arsenide, and the height of the potential barrier were experimentally determined.