V. V. Milenin

Mechanism of dislocation-governed charge transport in schottky diodes based on gallium nitride

A mechanism of charge transport in Au-TiBx-n-GaN Schottky diodes with a space charge region considerably exceeding the de Broglie wavelength in GaN is studied. Analysis of temperature dependences of current-voltage (I–V) characteristics of forward-biased Schottky barriers showed that, in the temperature range 80–380 K, the charge transport is performed by tunneling along dislocations intersecting the space charge region. Estimation of dislocation density ρ by the I–V characteristics, in accordance with a model of tunneling along the dislocation line, gives the value ρ ≈ 1.7 × 107 cm−2, which is close in magnitude to the dislocation density measured by X-ray diffractometry.

Au-TiBx-n-6H-SiC Schottky barrier diodes: Specific features of charge transport in rectifying and nonrectifying contacts

Mechanism of charge transport in a diode of a silicon carbide’s Schottky barrier formed by a quasi-amorphous interstitial phase TiBx on the surface of n-6H-SiC (0001) single crystals with an uncompensated donor (nitrogen) concentration of ∼1018 cm−3 and dislocation density of ∼(106–108) cm−2 has been studied. It is demonstrated that, at temperatures T ≲ 400 K, the charge transport is governed by the tunneling current along dislocations intersecting the space charge region. At T > 400 K, the mechanism of charge transport changes to a thermionic mechanism with a barrier height of ∼0.64 eV and ideality factor close to 1.3.

Effect of p-n junction overheating on degradation of silicon high-power pulsed IMPATT diodes

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C relative to an ambient medium. The temperature limit of junction overheating, above which IMPATT diodes rapidly degrade, was determined as 350°C. The presented results of X-ray phase analysis and depth profiles of Au-Pt-Ti-Pd-Si ohmic contact components confirm thermal limits of the IMPATT diode operating in the pulsed mode.

Temperature Dependence of the Contact Resistance of Ohmic Contacts to III-V Compounds with a High Dislocation Density

A new mechanism describing the rise in the contact resistance ρc of ohmic contacts to n-n+-n++-GaAs(GaP, GaN, InP) structures with increasing measurement temperature T, experimentally observed in the temperature range 100–400 K, is suggested on the basis of a theoretical analysis of the temperature dependence of ρc. Good agreement between the experimental and theoretical ρc(T) dependences is obtained and explained for a case where there is a high density of dislocations (on which metallic shunts are localized) in the near-contact region of the semiconductor.

Thermal-resistant TiB x -n-GaP Schottky diodes

The effect of rapid thermal annealing on the parameters of TiBx-n-GaP Schottky barriers and interphase interactions at the TiBx-GaP interface are studied. It is shown that the contact TiBx-n-GaP system features an increased thermal stability without varying the electrical parameters of the Schottky barrier at temperatures as high as 600°C.

Effect of microwave irradiation on the photoluminescence of bound excitons in CdTe:Cl single crystals

The effect of microwave radiation on the transformation of impurity-based structural complexes in CdTe:Cl single crystals is studied using low-temperature photoluminescence measurements. It is shown that microwave radiation activates ClTe centers, resulting in an increase in the intensity of photoluminescence line of excitons bound at the corresponding ClTe donor centers. A nonmonotonic dependence of the integrated photoluminescence intensity on the duration of microwave irradiation is observed. At the initial stage of microwave irradiation (t = 30 s), an increase in the integrated excitonic photoluminescence intensity is observed; as the duration of microwave irradiation is increased, the photoluminescence intensity decreases. The experimentally observed variations in the photoluminescence intensity are athermal in nature. The hypothetical mechanism of transformation of impurity-based structural complexes is described.

Specific features of recombination processes in CdTe films produced in different temperature conditions of growth and subsequent annealing

The steady-state and kinetic characteristics of photoconductivity and photoluminescence and the thermally stimulated conductivity spectra of the GdTe layers deposited by vacuum evaporation onto heated substrates are studied in relation to the substrate temperature. The measurements are carried out at temperatures, illuminations, and wavelengths ranging from 4.2 to 400 K, from 1010 to 1023 photon/cm2, and from0.4 to 2.5 μm, respectively. A certain optimal range of substrate temperatures Ts ≈ 450–550°C, at which the as-prepared layers exhibit a high resistivity, a high photosensitivity, and the best structural quality, is established. In the spectra of these layers, a new luminescence band at hvm = 1.09 eV is observed along with the known photoluminescence band at hvm = 1.42 eV. It is established that this new band is due to intracenter transitions rather than recombination transitions. The nature of radiative recombination centers in the layers is discussed. It is suggested that the d electrons of cations can be involved in the formation of chemical bonds of local centers in CdTe.

Microwave-radiation-induced structural transformations in homo- and heterogeneous GaAs-based systems

The effect of microwave irradiation (f = 2.45 GHz, 1.5 W/cm2, t = 1 or 2 min) on the reflectance and photoluminescence spectra of the epitaxial n-n+-GaAs and Au-n-n+-GaAs structures is studied. Short-term microwave irradiation is shown to cause long-term nonmonotonic changes in the spectral characteristics, which can result from the structure modification of the near-surface regions in the epitaxial films. The long-term changes of the optical spectra of the structures that occur after microwave irradiation are explained.

Radiation effects and interphase interactions in ohmic and barrier contacts to indium phosphide as induced by rapid thermal annealing and irradiation with γ-ray 60Co photons

The radiation resistance of Au-Pd-Ti-Pd-n++-InP ohmic contacts and Au-TiBx-n-n+-n++-InP barrier contacts—both initial and subjected to a rapid thermal annealing and irradiated with 60Co γ-ray photons with doses as high as 109 R—has been studied. Before and after external effects, the electrical characteristics of the barrier and ohmic contacts, distribution profiles for components, and phase composition in the metallization layers have been measured. In ohmic Pd-Ti-Pd-Au contacts subjected to rapid thermal annealing and irradiation, a significant distortion of the layered structure of metallization occurs; this distortion is caused by the thermal and irradiation-stimulated transport of Pd over the grain boundaries in polycrystalline Ti and Au films. However, the specific contact resistance ρc does not change appreciably, which is related to a comparatively unvaried composition of the contact-forming layer at the Pd-n+-InP interface. In the initial sample and the sample subjected to the rapid thermal annealing at T = 400°C with the Au-TiBx-n-n+-n++-InP barrier contacts and irradiated with the dose as high as 2 × 108 R, a layered structure of metallization is retained. After irradiation with the dose as high as 109 R, in the samples subjected to a rapid thermal annealing at T = 400°C, the layered structure of metallization becomes completely distorted; however, this structure is retained in the initial sample. The electrical properties of the contact structure appreciably degrade only after irradiation of the sample preliminarily subjected to a rapid thermal annealing at T = 400°C.

Effect of microwave treatment on the luminescence properties of CdS and CdTe:Cl Single Crystals

The effect of microwave radiation on the luminescence properties of CdS and CdTe:Cl single crystals is studied. It is established that the exposure of these semiconductors to short-term (≤30 s) microwave radiation substantially modifies their impurity and defect structure. The mechanisms of transformation of the defect subsystem of II–VI single crystals upon microwave treatment are discussed. It is shown that the experimentally observed changes are defined by the nonthermal effects of microwave radiation at a power density of 7.5 W cm–2; at 90 W cm–2, nonthermal effects are prevailing.