Subnanosecond impact-ionization switching of silicon structures without <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> junctions

It is shown that an application of a fast-rising high-voltage pulse to an n ⁺–n–n ⁺ silicon structure leads to subnanosecond avalanche breakdown, generation of electron–hole plasma throughout the entire structure, and structure switching to the conducting state in a time of about 100 ps. The predicted effect is similar to the delayed avalanche breakdown of reverse-biased p ⁺–n–n ⁺ diode structures; however, it is implemented in a structure without p–n junctions.     

Investigation of the thermal stability of picosecond gallium arsenide dynistor switches

The operation of GaAs n⁺-p-i-n ⁰-p ⁺ dynistor structures has been demonstrated experimentally under conditions of reversible avalanche breakdown at temperatures up to 200 °C with switching times remaining under 140 ps. A numerical simulation refined the influence of various parameters of the semiconductor on the temperature dependence of the switching characteristics. Pis’ma Zh. Tekh. Fiz. 24, 73–78 (August 12, 1998)     

Experimental Observation of Delayed Impact-Ionization Avalanche Breakdown in Semiconductor Structures without p–n Junctions

We have experimentally studied the dynamics of impact-ionization switching in semiconductor structures without p–n junctions when subnanosecond high-voltage pulses are applied. Silicon n⁺–n–n⁺ type structures and volume ZnSe samples with planar ohmic contacts exhibit reversible avalanche switching to the conducting state within about 200 ps, which resembles the well-known phenomenon of delayed avalanche breakdown in reverse-biased p⁺–n–n⁺ diode structures. Experimental data are compared to the results of numerical simulations.

     

Defects in heteroepitaxial CdHgTe/Si layers and their behavior under conditions of implanted p +-n photodiode structure formation

The impurity-defect structure of heteroepitaxial Cd _x Hg_{1 ? x} Te/Si (0.35 < x < 0.39) layers grown by molecular beam epitaxy for the creation of arsenic-ion-implanted p ⁺-n junctions has been studied by the photoluminescence method. It is established that full realization of the possibilities of p ⁺-on-n photodiode structures based on the CdHgTe/Si system is hindered by uncontrolled doping of the material that leads to the formation of both shallow (impurity level energy ～10 meV) and deep (～50 meV) acceptor levels.     

Parameters of silicon carbide diode avalanche shapers for the picosecond range

Parameters of ultrafast avalanche switching of high-voltage diode structures based on 4H-SiC have been estimated theoretically. The calculation was carried out using the analytical theory of the impact ionization wave of the TRAPATT type, which makes it possible to determine the main characteristics of a wave for arbitrary dependences of the impact ionization coefficients and carrier drift velocity on electric field. It is shown that, for a high-voltage (1–10 kV) 4H-SiC structure, the time of switching from the blocking to the conducting state is ~10 ps, which is an order of magnitude shorter than that for a Si structure with the same stationary breakdown voltage, and the concentration of the electron-hole plasma created by the wave is two orders of magnitude higher. Picosecond switching times can be reached for 4H-SiC structures with a stationary breakdown voltage exceeding 10 kV.     

Features of changes in electrical parameters of silicon p-n structures upon high-temperature electron irradiation

The effect of the temperature mode of 4-MeV electron irradiation on the change in the basic electrophysical characteristics of silicon diffused p ⁺-n-n ⁺ structures has been studied. It has been shown that the temperature of the crystal and integrated intensity during irradiation have a significant effect on the parameters of formation of radiation defects and the pattern of their distribution in different regions of silicon p ⁺-n-n ⁺ structures.     

Investigation of the process of voltage distribution over elements of a high-power semiconductor current interrupter

The process of voltage distribution over serially connected elements of a high-power semiconductor current interrupter in the stage of current breakage is studied within the framework of a previously developed physicomathematical model. It is established that a mechanism is operative that provides for the voltage drop leveling between unit structures of the p ⁺-p-n-n ⁺ type with various depths X _p of the p-n junctions. The mechanism is related to the fact that the formation of a strong field region on the stage of current breakage in the unit structures with larger X _p begins later, but the expansion of this region proceeds faster than the same processes in the units with smaller X _p .     

Studying electric field profiles in GaAs-based detector structures by Kelvin probe force microscopy

The method of scanning Kelvin probe force microscopy has been used to study the electric field distribution in GaAs-based p ⁺-π-n-n ⁺ detector structures. In the active layer volume, two maxima in the field strength profiles have been found, which are localized in the regions of p ⁺-π and π-n junctions. A volt-age drop on the π-n junction expands the region of collection of nonequilibrium holes, thus increasing the charge collection efficiency for the absorption of γ photons with an energy of 59.5 keV.     

Performance of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> 4H-SiC film nuclear radiation detectors for operation at elevated temperatures (375 °C)

The spectrometric characteristics of nuclear radiation detectors based on 4H-SiC films with iondoped p ⁺-n junctions have been studied for the first time in a temperature range from 25 to 375°C. The experiments with 5.8-MeV α particles were performed in a high-temperature chamber of special design. Factors related to the structural characteristics of both the initial silicon carbide and the ion-doped p ⁺-n junctions are established, which limit from above the temperature interval of detector operation in a spectrometric regime. An increase in the efficiency of the diffusion-drift charge transport with increasing temperature has been observed, which is explained by an increase in the diffusion length of minority carriers.     

Photovoltaic X-ray detectors based on epitaxial GaAs structures

A new type of the photovoltaic X-ray detector based on epitaxial p ⁺-n-n′-n ⁺ GaAs structures is proposed, which provides for a high efficiency of charge carrier collection in a nonbiased operation regime at room temperature. The GaAs structures were grown by vapor phase epitaxy on heavily doped n ⁺-GaAs substrates. The X-ray sensitivity range covers the effective energies from 8 to 120 keV. The maximum output signal in the short-circuit regime is 30 μA min/(Gy cm²). The detector response to γ-radiation from a ¹³⁷Cs[660 keV] radioactive isotope was measured.     

Forming n-p junctions based on p-CdHgTe with low charge carrier density

The first results on the formation of n ⁺-p photodiodes with a long-wavelength boundary at λ_0.5 = 10.6 μm based on p-CdHgTe epilayers with a hole density of 3.3 × 10¹⁴ cm^?3 are presented. The CdHgTe layers were obtained by molecular beam epitaxy and exhibited p-type conduction in the as-grown state. The hole density and mobility were determined by means of the mobility spectrum technique. The photodiode structures were prepared by B⁺ ion implantation into as-grown p-CdHgTe epilayers without additional annealing. The R ₀ A product for the n ⁺-p photodiodes obtained is about 20 Θ cm² at 77 K.     

A study of vacuum-ultraviolet stability of silicon photodiodes

Silicon photodiodes have been tested for resistance to vacuum-ultraviolet radiation at 121.6 nm. The responsivities of the p-n and n-p photodiodes under study were found to degrade by tens of percent at a VUV radiation dose on the order of tens of mJ/cm². The effect of reversible photocurrent relaxation has been observed in detectors based on n-p structures.     

GaAs p-i-n structures for X-ray detectors grown on Ge and GaAs substrates

Features of the creation of gallium arsenide (GaAs) p-i-n structures on germanium substrates are considered. Optimum regimes for growth of thick GaAs layers by hydride-chloride vapor phase epitaxy (HVPE) on Ge substrates are established, which allow high-quality p-i-n structures with characteristics close to those reached by homoepitaxy to be obtained. The spectra of exciton photoluminescence have been measured for ultrahigh-purity GaAs layers of various thicknesses grown under differing HVPE conditions.     

Photoelectric and electrical properties of a reverse-biased p-Si/n-CdS/n +-CdS heterostructure

We have demonstrated a photosensitive p-Si/n-CdS/n ⁺-CdS structure. A reverse bias voltage applied to this structure leads to electron injection from the narrow-band-gap material p-Si to the high-resistivity, wide-band-gap semiconductor n-CdS. Evidence is presented for mutual compensation of opposite drift and diffusion flows of charge carriers in this structure. At current densities in the range I ～ 10^?8 to 10^?7 A/cm², the opposite drift and diffusion flows of nonequilibrium minority charge carriers cause the photosensitivity of the structure to change sign in both the short- and long-wavelength regions of the spectrum. The mutual compensation of the opposite drift and diffusion flows at current densities on the order of ～10⁶ A/cm² leads to sublinear behavior of the reverse current-voltage characteristic in a wide range of bias voltages.     

A magnetically controlled LED with S-shaped current-voltage characteristic

A p-i-n light-emitting diode (LED) structure with InGaAs/GaAs quantum wells has been manufactured by combining the vapor phase epitaxy and laser ablation methods. The obtained heterostructures exhibit a negative differential resistance and the magnetodiode effect at 77 K. The proposed LED structure admits (i) switching from the low- to high-resistance state by applied pulsed bias voltage and (ii) electroluminescence quenching by external magnetic field.     

Charge Carrier Transport and Deep Levels Recharge in Avalanche S-Diodes Based on GaAs

Carrier transport and deep-level recharging in semiconductor avalanche S-diode structures have been investigated. Gallium-arsenide n⁺–π–ν–n structures with the diffusion distribution of deep iron acceptors have been studied. It has been found by solving the continuity and Poisson equations with the use of a commercial software that the electron injection affects the avalanche breakdown voltage and the spacecharge region broadens due to capture of avalanche holes on negative iron ions in the π-region. It is demonstrated by comparing the results of numerical calculation with the experimental data that the S-shaped I–V characteristic of the diffusion avalanche S-diodes cannot be explained within the previously proposed mechanism of capture of avalanche holes on the deep iron levels.     

Bias frequency dependence of pn junction charging damage induced by plasma processing

Plasma-induced charging damage to pn junction in metal-oxide-semiconductor field-effect transistors (MOSFETs) was studied by using an inductively coupled plasma (ICP) reactor with Ar gas. The junction leakage current (I_leak) was measured for various source/drain to well in MOSFETs and simple diode structures. Two different rf bias frequencies, 13.56 MHz and 400 kHz, were utilized to investigate the effect of frequency on an increase in I_leak. The I_leak of n⁺/p and p⁺/n junctions was found to increase by a plasma treatment. In particular, more severe damage was observed for n⁺/p junction in both n-channel MOSFETs and the diodes. These observed results imply that plasma plays a role primarily as a positive current source. With regard to the rf bias frequency effects, samples exposed to the 400-kHz plasma were found to suffer from larger I_leak than those to the 13.56 MHz. From capacitance-voltage (C-V) measurement of junction capacitance changes, we also clarified that the observed increase in I_leak was attributed to the defect density at pn junction created by the plasma charging damage.     

Analysis of the structural parameters of an a-Si : H n+-i-n+ structure by numerical simulations

In this study, we discuss measurements of the J–V characteristics of an a-Si : H n⁺-i-n⁺ structure, and the results of numerical simulation using the AMPS-1D simulation program. Application of the AMPS simulation model to the sample structures considered allows us to determine the structural properties of the a-Si : H n⁺-i-n⁺ structure. The one-dimensional simulation program was examined in n⁺-i-n⁺ structures with different qualities and thicknesses of the i-layer. We find that the n⁺/i interface is more abrupt for a device with a high density of states (DOS), resulting in high values of the activation energy (E _act). In contrast, thin samples of good quality (low DOS) give low values of E _act. Analysis by numerical modeling confirms the experimental results.     

p-type doping of ZnO by means of high-density inductively coupled plasmas

A custom-designed inductively coupled plasma assisted radio-frequency magnetron sputtering deposition system has been used to fabricate N-doped p-type ZnO (ZnO:N) thin films on glass substrates from a sintered ZnO target in a reactive Ar + N₂ gas mixture. X-ray diffraction and scanning electron microscopy analyses show that the ZnO:N films feature a hexagonal crystal structure with a preferential (002) crystallographic orientation and grow as vertical columnar structures. Hall effect and X-ray photoelectron spectroscopy analyses show that N-doped ZnO thin films are p-type with a hole concentration of 3.32 × 10¹⁸ cm^− 3 and mobility of 1.31 cm² V^− 1 s^− 1. The current-voltage measurement of the two-layer structured ZnO p-n homojunction clearly reveals the rectifying ability of the p-n junction. The achievement of p-type ZnO:N thin films is attributed to the high dissociation ability of the high-density inductively coupled plasma source and effective plasma-surface interactions during the growth process.     

The effect of hydrogenation on the photoconductivity of ion-doped gallium arsenide structures

It was found that the hydrogenation of ion-doped n ⁺-n-n _i -GaAs structures in atomic hydrogen increases the rate of conductivity relaxation in the doped layers, decreases the effect of bias voltage applied to the n ⁺-GaAs layer on the photoconductivity, and improves characteristics of the Schottky barrier transistors and the related integrated circuits. These phenomena are probably due to the formation of hydrogen complexes with electrically active centers in GaAs.