N. M. Shmidt

Point defects in gamma-irradiated n-GaN

Radiation-induced point defects and their annealing in silicon-doped n-GaN have been investigated by means of Hall effect measurements and Raman spectroscopy. Correlated compensation effects due to simultaneous introduction of donor and acceptor centres are observed in irradiated n-GaN. The defect production rate is dependent on the dopant concentration. This means that the model of all native defects immobile at room temperature is not true. The behaviour of radiation-induced defects upon heating is complicated, exhibiting two prominent stages of reverse annealing. The presence of radiation defects is still observable after annealing to T = 750 °C.

Radiation-induced defects in n-type GaN and InN

The electrical properties of the n-GaN and n-InN, subjected to proton irradiation, are studied. The irradiation of the n-InN results in an increasing concentration of charge carriers, whereas strong compensation effects take place in the proton-irradiated n-GaN. The annealing behavior of the radiation-induced defects in both materials is discussed briefly.

UV LEDs for high-current operation

In this paper we report on results of development of ultraviolet light-emitting diodes (UV LEDs) based on GaN/AlGaN heterostructures grown on Al2O3 (0001) substrates by chloride-hydride vapour phase epitaxy (CHVPE). Both UV LED heterostructures and packaged dies are investigated. UV LEDs proved performance capability at current density up to 125 A/cm2 and revealed wall-plug efficiency (WPE) of 1.5% at operating current of 20 mA.

Failure mechanisms in blue InGaN/GaN LEDs for high power operation

Unpredictable fast failure of blue power InGaN/GaN LEDs is caused by redistribution of In under action of injection currents between nano-scale regions of InGaN alloy with non-equilibrium composition. Unreliable LEDs can be recognized by the increase in forward current values at U < 2 V which is not accompanied by simultaneous reversed current increase during short aging tests (less than 100 h).

Study of the effect of irradiation with the SEM electron beam on cathodoluminescence and the induced current in InGaN/GaN structures with multiple quantum wells

The effect of irradiation with low-energy electrons on the optical and electric properties of InGaN/GaN-based LED structures with multiple quantum wells is studied using the methods of cathodoluminescence (CL) and electron-beam induced current (EBIC). It is shown that such irradiation leads to a change in both the electric and optical properties of these structures. The fitting of the dependences of the induced-current signal on the beam energy makes it possible to show that irradiation leads to the suppression of the recombination in the upper p-GaN layer, to a decrease in the probability of transition of charge carriers through the active region of the structure with quantum wells, and to a increase in the effective concentration of donors in the active region. These changes make it possible to explain the increase in the integral CL intensity, but it does not explain the change in its spectrum

EBIC characterization of light emitting structures based on GaN

EBIC investigations of light-emitting structures based on InGaN/GaN MQW with different numbers of wells have been carried out. A pronounced dependence of collection efficiency on quantum-well number is observed. A comparison with apparent carrier profiles calculated from C-V curves reveals a correlation between the collection efficiency and location of quantum well inside the depletion region. Defects producing bright EBIC contrast are revealed in the structure with five quantum wells. This contrast is associated with defects locally decreasing the excess carrier recombination inside quantum wells.

Peculiarities of the initial stage of Zn diffusion into InP from polymer spin-on films

Abstract The initial stage of Zn diffusion into InP from polymer spin-on films has been investigated. A high concentration of microdefects and extended defects in the near-surface region (depth up to 1 μm), anomalously deep penetration of Zn atoms with a diffusivity nearly independent of temperature and a low activation degree of diffused Zn have been found. A kick-out mechanism is thought to be dominant at the initial stage.

Localized states in the active region of blue LEDs related to a system of extended defects

Blue light-emitting diodes (LEDs) based on InGaN/GaN quantum wells (QWs) with different characters of the system of extended defects (SEDs) threading through the active region have been studied using the current-voltage (I–U), capacitance-voltage (C–V), and deep-level transient spectroscopy (DLTS) measurements in the dark and under illumination with white light in a temperature range from 100 to 450 K. The DLTS curves exhibit broad E1 and E2 peaks with amplitudes dependent on the illumination. This behavior can be explained assuming the presence of localized states related to SEDs in the active region of the LED. The LEDs with more developed SEDs are characterized by a greater concentration of donor-type traps, which leads to an increase in the density of free charge carriers in QWs, which screen the electron-hole interaction. This circumstance can be among the factors responsible for a severalfold decrease in the quantum efficiency of such LEDs.

Rare-earth elements in the technology of III–V compounds and devices based on these compounds

The results of our studies concerned with the use of rare-earth elements in the liquid-phase epitaxial technology of the InP, InGaAsP, InGaAs, and GaP compounds and with the fabrication of various optoelectronic and microelectronic devices and structures based on these compounds are summarized. The results related to the surface gettering of GaAs with the films of rare-earth elements in order to obtain a high-resistivity material for various purposes are also reported.

Behavior of electrically active point defects in irradiated MOCVD n-GaN

Abstract Formation and annealing of radiation-induced defects in doped and nominally undoped n-GaN are investigated by means of electrical measurements and Raman spectroscopy. The production rate of defects turned out to be dependent on the dopant concentration. This suggests that at least one kind of native defects is involved in impurity–defect interactions at room temperature. Two prominent stages of defect annealing are revealed. The annealing processes at T ≥100°C are associated with mobile native defects. A considerable fraction of radiation defects is still present in the materials after annealing to T ≥750°C.