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The results of experimental investigation of forward currentvoltage characteristics of InGaN/GaN multiple quantum well light-emitting diodes are presented. A new model for explaining the complex current dependence on voltage is proposed. The model is based on the assumption of space charge limited current, and ballistic overflow of electrons through the multiple quantum well region. It is shown that electrons are captured in the shallow traps while transferring through the active region. The results of measurements indicate that the activation energy of traps decreases with a temperature decrease, which corresponds to the theory of hopping in exponential band tails.

The article is concerned with a detailed switching delay effect exhibited by avalanche S-diodes-superfast GaAs closing switches doped with deep Fe centers. The current and voltage time dependences are simulated in a simplified generator. The dynamic electric field and charge profiles in the structures are calculated. This article describes an impact that Fe capture cross sections of free charge carriers have on delayed switching. The simulation results show that delayed switching is associated with deep center recharging in a double injection mode due to three different processes. There are two different delay mechanisms to be herewith distinguished. A delay effect is experimentally viewed to control the dynamic switching voltage (and the avalanche breakdown voltage) using constant voltage adjustment capability enabled by a triggering circuit supply. The authors demonstrate the way it is possible to adjust the amplitude of current nanosecond pulses in the range of 20-45 A through a lidar transmitter circuit with a semiconductor laser and nonoptimized S-diode. The findings are consistent with the results of numerical simulation.

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Application of high-resistance GaAs for the formation of ionizing radiation detectors calls for investigation of physical properties of this material. Studying the photoelectrical properties makes it possible to establish the recombination mechanisms of charge carriers and peculiarities of their transport in the electric fields as well as to evaluate the charge-carrier lifetimes. In this work, the results of studying the photoconductivity and Hall photoeffect are discussed for high-resistance GaAs doped by chromium diffusion. A typical lux-ampere characteristic is shown to consist of two parts: a superlinear part and a sublinear one. Changes in the Hall mobility under illumination are studied. A number of simplifications are made and the electron (τ n ) and hole (τ p ) lifetimes are estimated for high and low excitation levels. It is found that τ p > τ n . It is shown that the photoelectrical properties of high-resistance GaAs:Cr can be explained using the model of "curved bands." It is assumed that the potential barriers are transformed under photoexcitation.

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