The results of the study of GaP pn structures at high temperature are presented. The previously obtained results of the experimental study of band-edge injection electroluminescence at high temperatures of pn homostructures based on silicon carbide of different polytypes, fabricated by container-free liquid-phase epitaxy (6H-, 4H-SiC), sublimation epitaxy (6H-, 4H-, 3C-SiC), sublimation epitaxy and ion implantation (6H-, 4H-SiC), vapor-phase epitaxy (4H-SiC), vapor -phase epitaxy and ion implantation (4H-SiC) and based on GaN, fabricated by the chloride-hydride gas-phase epitaxy, are systematized. In the temperature range of 300 divided by (650-800) K, such parameters of band-edge injection electroluminescence as the spectral position of the maximum relative to the band gap, shape of the spectral band, the type of the dependence of the radiation intensity on the current and temperature were determined. It was found that, with the proximity of the main parameters of electroluminescence, the band-edge injection electroluminescence in SiC of all the studied polytypes differs from that in GaN and GaP in the nature of the temperature dependence at T > 300 K: an increase with increasing temperature in pn structures based on SiC and a decrease in semiconductors based on A(3)B(5). Silicon carbide can be considered as a material for high-temperature LED electronics.

The effect of isochronous annealing in vacuum at temperatures of 100–400°C on the forward and reverse current-voltage characteristics of Cr–SiC(4H) Schottky diodes is studied. Diodes of different sizes are manufactured using the same technology based on one lightly doped ( 4 × 1014 cm–3) epitaxial layer. The current-voltage characteristics are close to ideal in all cases, but their significant spread before annealing, a decrease in the spread, and a shift to the low-voltage region as a result of annealing at 400°C were found. It is assumed that the main diode is in all cases is shunted by a parasitic diode, the barrier height of which is reduced as a result of annealing.

A study of injection electroluminescence of GaN pn homostructures produced by chloride–hydride gas-phase epitaxy is presented. The epitaxial layers are doped with silicon and magnesium to obtain n-type (doping level 5 × 1018 cm−3) and p-type (doping level 1.6 × 1018 cm−3) conductivity, respectively. Injection electroluminescence was observed in the forward current range of 3 × 10−4–2 × 10−2 A (0.4–30 A/cm2) at temperatures of 300–720 K, when the current was apparently due to recombination in the space-charge region of the pn junction through a deep level near the middle of the bandgap. Two bands are observed in the electroluminescence spectra at 300 K: the band edge (shortwave) in the near ultraviolet region (hνmax ∼3.33 eV) and in the yellow region of the spectrum (hνmax ∼2.15 eV). For band-edge electroluminescence, it was found that when heated from 300 K, its intensity decreases with an activation energy of about 80 meV; the maximum shifts linearly to the long-wavelength region with a temperature with a slope of “−5.4 × 10−4 eV/K” and the energy at the maximum is 66 meV less than the bandgap; and the full width at half-maximum with heating to 430 K decreases from 235 to ∼145 meV, maintains this value to a temperature of 550 K, and then increases to 195 meV at 650 K. The quenching of band-edge injection electroluminescence at temperatures higher than room temperature may be associated with a decrease in the lifetime of nonequilibrium charge carriers during heating.

A study was conducted on the effect of low-dose ( 1016 cm–2) irradiation with electrons with an energy of 0.9 MeV and subsequent isochronous annealing at temperatures up to 550°C on the current-voltage characteristics of commercial rectifier diodes based on 4H-SiC with a doping level of (3–7) × 1015 cm–3. The previously established effect of increasing series resistance Rs of diodes under irradiation, the numerical value of the threshold dose of irradiation, and the effect of the spread of the value of Rs of identical diodes at the same dose of radiation have been confirmed. For the first time, isochronous annealing (without passing current during annealing) was performed at temperatures up to 550°C, significantly exceeding the maximum operating temperatures of the diodes. It has been shown that starting from temperatures ≥200°C the annealing of defects is observed, which is expressed in a decrease in the value of Rs at room temperature down to pre-irradiation values. Annealing also leads to a decrease in the reverse breakdown current.

The effect of annealing on the parameters of 4H-SiC Schottky diodes irradiated with electrons at high temperatures has been studied for the first time. The electron energy was 0.9 MeV. The irradiation was carried out at temperatures of 23, 300, and 500oС at fluences  in the range 1×1016 – 1.3×1017 cm-2. The results of annealing after the irradiation at high temperatures are qualitatively different from the results of annealing after conventional irradiation at room temperature with the same fluencies. The results obtained indicate that the spectrum of radiation defects introduced into SiC under a high-temperature (“hot”) irradiation differs significantly from that of defects introduced by irradiation at room temperature. At irradiation temperatures of 300 and 500°C and large, the effect of "reverse annealing" was revealed, when the base resistance grows rather than falling as a result of annealing.

The effect of annealing on the parameters of 4H-SiC Schottky diodes irradiated with electrons at a high temperature is studied for the first time. The electron energy is 0.9 MeV, irradiation is carried out at temperatures of 23, 300, and 500°C with fluences Φ in the 1 × 1016–1.3 × 1017 cm–2 range. The results of annealing samples irradiated at high temperatures differ qualitatively from the results of annealing samples irradiated with the same fluence at room temperature. The results indicate that, under high-temperature (“hot”) irradiation, the spectrum of radiation-induced defects introduced in SiC differs significantly from the spectrum of defects introduced at room temperature. The effect of reverse annealing, when the resistance of the base of the diode does not fall but increases as a result of annealing, was discovered for large values of Φ at irradiation temperatures of 300 and 500°C.

For the first time, a comparative study of the effect of electron and proton irradiation at a temperature of 20–500°C on the characteristics of semiconductor devices based on silicon carbide, i.e., commercial high-voltage 4H-SiC Schottky diodes, is carried out. The diodes are irradiated with 15-MeV protons and 0.9‑MeV electrons. It is found that the most sensitive parameter, which determines the radiation resistance of devices, is the base resistance, which monotonically increases with the radiation dose D. It is shown that, under low-temperature (“cold”) irradiation, the efficiency of compensation of a semiconductor by proton irradiation is about 400 times higher than the efficiency of electron irradiation. Under “hot” (high temperature) irradiation, the radiation resistance of diodes is several times higher than the resistance of diodes under “cold” irradiation. The rate of formation of deep centers in the upper half of the band gap of silicon carbide decreased with increasing irradiation temperature.

Forward and reverse current-voltage (IV) characteristics of Cr-SiC (4H) Schottky diodes based on epitaxial layers with doping (1-3)· 10 15 cm -3 were studied in the temperature range of 300-550 K. It is shown that in many cases the IV characteristics are close to ideal, but a significant spread of the forward IV characteristics of diodes manufactured in the same way on the same epitaxial layer was found, probably due to the spread of the Schottky barrier heights reaching 0.3 eV. Heating of the diode, as well as packaging, can also change the Schottky barrier height. An alternative explanation suggests the presence of a powerful shunt.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063782621030192

We report the results of a study into the impact of irradiation with 0.9 MeV electrons on the main properties of 4H-SiC MOSFETs of 1.2 kV class at irradiation doses Phi within the range from 0.125 to 3 MGy (fluence F from 75 x 10(14) to 1.2 x 10(16) cm(-2)). The effects of irradiation on the threshold voltage, leakage current, output characteristics, and channel electron mobility have been studied. The results obtained are compared with the known data on the irradiation of high-voltage 4H-SiC MOSFETs with 4.5 MeV electrons and gamma-photons from a(60)Co source. It is shown that the parameter variations of the MOSFETs under influence of irradiation depends on both the dose and the electron energy. A high radiation hardness of the structures under study has been demonstrated.

For the first time, the effect of irradiation at high temperature (“hot irradiation”) by protons on the capacitance – voltage and current – ​​voltage characteristics of silicon carbide based semiconductor devices was studied. We investigated commercial high-voltage (blocking voltage of 1700 V) integrated 4H-SiC Schottky diodes. Irradiation was carried out by protons with an energy of 15 MeV at temperatures of 20-400 ° C. It has been established that the most sensitive to radiation parameter determining the radiation resistance of devices is the ohmic resistance of the base, which increases monotonically with increasing radiation dose D. It is shown that during “hot” irradiation, the radiation resistance of diodes significantly exceeds the resistance of diodes in low-temperature (“cold”) irradiation . It was concluded that, with increasing irradiation temperature, the rate of formation of deep centers in the upper half of the band gap of silicon carbide decreases.

The processing technique for microwave p – i – n diodes based on SiC (silicon carbide) has been developed. Based on these diodes, switches in the 3-cm range have been fabricated. It has been shown that the working power of the developed switches is about 10 times higher than that based on Si diodes at the same base thickness, which is equal to 5 μm. The ways of further improvement of the processing technique of these devices have been suggested.

The influence of proton irradiation at high temperatures (“hot” irradiation) on the capacitance–voltage and current–voltage characteristics of semiconductor devices based on silicon carbide has been studied for the first time. The experiments were performed on commercial high-voltage integrated 4H-SiC Schottky diodes with a blocking voltage of 1700 V, which were irradiated by 15-MeV protons at temperatures within 20–400°C. It is established that the most sensitive parameter determining the degree of radiation-induced damage is the ohmic resistance of the base, which monotonically increases with irradiation dose D . Under “hot” irradiation conditions, the radiation resistance of diodes is significantly higher as compared to that observed in the case of low-temperature (“cold”) irradiation. It is concluded that an increase in the temperature is accompanied by a decrease in the rate of formation of deep defect centers in the upper half of the bandgap of silicon carbide.

Исследованы прямые и обратные вольт-амперные характеристики коммерческих выпрямительных диодов на основе барьера Шоттки к 4H-SiC в диапазоне температур 20-370oС; максимальный ток составлял 10-20 мА, максимальное напряжение 10-100 В. Установлено, что диоды можно считать близкими к идеальным с высотой барьера Шоттки ~1.5 эВ, при этом прямой ток во всем диапазоне температур, а обратный ток при высоких температурах в значительной степени обусловлены термоэлектронной эмиссией. Верхняя граница диапазона рабочих температур выпрямительных диодов Шоттки на основе 4H-SiC при исследуемых токах и напряжениях примерно соответствует фундаментальной границе, определяемой высотой барьера, и в представленном эксперименте достигает 370oC. Ключевые слова: карбид кремния, выпрямительный диод, барьер Шоттки, высокая температура.

Представлены результаты исследования различными методиками исходных структур n-4H-SiC, представляющих высоколегированную n+-подложку с выращенным химическим осаждением из газовой фазы эпитаксиальным слоем толщиной 5 мкм. Концентрация носителей заряда в эпитаксиальном слое в диапазоне Nd-Na=(1-50)·1014 см-3. Привлекая результаты рентгеноструктурного анализа, было установлено, что для получения эффективных 4H-SiC ультрафиолетовых фотоприемников желательно иметь структуры эпитаксиальных слоев, в которых наблюдается эффект геттерирования точечных дефектов, что приводит к росту времени жизни носителей заряда и увеличению значений квантовой эффективности. Фоточувствительность исследованных образцов значительно зависит от степени дефектности в CVD эпитаксиальном слое, приводящей к изменению времени жизни носителей заряда и, как следствие, к изменению квантовой эффективности 4H-SiC ультрафиолетовых фотоприемников. Ключевые слова: карбид кремния, рентгеноструктурный анализ, эффект геттерирования, квантовая эффективность.

Forward and reverse current-voltage (I-V) characteristics of commercial rectifying Schottky diodes (SDs) based on silicon carbide (4H-SiC, base layer doping level 3·1015 cm-3) have been studied under irradiation with 0.9 MeV electrons and 15 MeV protons. The starting diodes were characterized by a barrier height of ~1.5 eV and nearly ideal forward and reverse I-V characteristics. It was found that, at doses exceeding the threshold dose Dth, the series differential resistance Rs of the diodes grows as Rs ~ Dm (m = 10-15) and shows no tendency toward saturation. Dth ≈7·1015 cm-2 under electron irradiation, and Dth ≈ 4·1013 cm-2 in the case of irradiation with protons. Heating to 200oC results in that Rs decreases with activation energy of ~1.1 eV and Rs is partly annealed-out with activation energy of ~0.7 eV. The starting Schottky diodes changes only slightly under irradiation, but, possibly, the irradiation leads to an over-compensation of the n-type layer and formation of an additional barrier in the form of a pn junction.

Разработана технология СВЧ p-i-n-диодов на основе карбида кремния (SiC). С использованием данных диодов изготовлены переключатели для трехсантиметрового диапазона. Показано, что разработанные приборы по величине рабочей мощности примерно в 10 раз превышают рабочую мощность переключателей на базе Si-диодов при одинаковой толщине базы, равной 5 μm. Намечены пути дальнейшей оптимизации технологии данных приборов. Ключевые слова: карбид кремния, СВЧ диоды, модуляторы, переключатели, аттенюаторы.

Исследовано изменение вольт-амперных характеристик и величины Nd-Na в базе диодов Шоттки и JBS-диодов на основе 4H-SiC при их облучении электронами с энергией О,9 МэВ и протонами с энергией 15 МэВП, показано, что исследованные диоды Шоттки сохраняли выпрямляющие вольт-амперные характеристики вплоть до доз облучения ~1О17 см-2. Установлено, что радиационная стойкость диодов Шоттки на основе SiC существенно превосходит радиационную стойкость кремниевых p-i-n-диодов с аналогичными напряжениями пробоя. Впервые исследовано влияние протонного облучения (энергия протонов 15 МэВ) на электрофизические и шумовые параметры 4H-SiC мощных вертикальных MOSFET.

Impact of 15 MeV proton irradiation on electrical characteristics and low frequency noise has been studied in high-power vertical 4H-SiC MOSFETs of 1.2 kV-class at doses 1012 £ F £ 1014 cm-2. The maximum value of the field-effect mobility µFЕ depends weakly on F up to F = 2×1013 cm-2. At F = 4×1013 cm-2, the character of the µFЕ(Vg) dependence changes radically. The maximum µFЕ decreases approximately threefold. The dose Fcr corresponding to the complete degradation of the device is about 1014 cm-2. It can be estimated as Fcr» he/n0, where he is the electron removal rate and n0 is the initial electron concentration in the drift layer. In the entire frequency range of analysis f, gate voltages, and drain-source biases, the frequency dependence of the current spectral noise density SI(f) follows the law SI ~ 1/f. From the data of noise spectroscopy, the density of traps in the gate oxide Ntv has been estimated. In non-irradiated structures, Ntv » 5.4×1018 cm-3eV-1. At Ф = 6×1013 cm-2, the Ntv value increases to Ntv » 7.2×1019cm-3eV-1. The non-monotonic behavior of the output current Id and the level of low frequency noise on dose F has been demonstrated.

Comparative studies of the structural, electrophysical properties and spectral sensitivity of 4 H -SiC photodetectors of ultraviolet radiation in the spectral range of 200-400 nm were carried out before and after electron irradiations. Photodetectors with Cr Schottky barriers with thickness of 20 nm and 8 mm diameter were formed on n -4 H -SiC CVD epitaxial layers with a thickness of 5 μm and concentration N d -N a = (1-4) х10 14 cm -3 . Cr/4 H -SiC photodiodes were irradiated by electrons at 0.9 MeV energy with doses (0.2-1) x10 16 cm -2 .