O. Yu. Serebrennikova

Excess leakage currents in high-voltage 4H-SiC Schottky diodes

The high-voltage 4H-SiC Schottky diodes are fabricated with a nickel barrier and a guard system in the form of “floating” planar p-n junctions. The analysis of I–V characteristics measured in a wide temperature range shows that the forward current is caused by thermionic emission; however, the current is “excessive” in the reverse direction. It is assumed that the reverse current flows locally through the points of the penetrating-dislocation outcrop to the Ni-SiC interface. The shape of reverse I–V characteristics makes it possible to conclude that the electron transport is governed by the monopolar-injection mechanism (the space-charge limited current) with participation of capture traps.

Electrical properties of Pd-oxide-InP structures

Pd-anodic oxide-InP metal-oxide-semiconductor (MOS) structures are fabricated to develop a hydrogen sensor capable of effectively operating at room temperature. The conduction mechanisms of the structures at 100–300 K are studied. It is found that the oxide behaves as ohmic resistance and the rectifying properties of the structures are determined by the potential barrier at the oxide-InP interface with the thermal-tunneling charge transport mechanism. The structures greatly change their characteristics in the presence of hydrogen in the ambient medium.

Photodiodes based on InAs/InAs0.88Sb0.12/InAsSbP heterostructures for 2.5–4.9 μm spectral range

Photodiodes with a photosensitive area diameter of 0.3 mm operating at room temperature in a middle-IR (2.5–4.9 μm) wavelength range have been created based on InAs/InAs0.94Sb0.06/InAsSbP/InAs0.88Sb0.12/InAsSbP/InAs heterostructures grown by liquid phase epitaxy. Distinguishing features of the proposed photodiodes are a high monochromatic responsivity, which reaches a maximum of 0.6–0.8 A/W at λmax = 4.0–4.6 μm, and a low dark current density of (1.3–7.5) × 10−2 A/cm2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 700–800 Ω. The detection ability of photodiodes in the spectral interval of maximum sensitivity reaches (5–8) × 108 cm Hz1/2 W−1.

LEDs based on InAs/InAsSb heterostructures for CO2 spectroscopy (λ = 4.3 μm)

Light-emitting diodes (LEDs) operating in a 4.1–4.3 μm wavelength range have been created on the basis of InAs/InAsSb heterostructures grown by metalorganic vapor-phase epitaxy. The output radiation power of LEDs is increased using flip-chip design. Investigation of the electrolumuinescent properties of LEDs with smooth and profiled output edge surface showed that the latter LEDs possess a greater efficiency, which is related to an increase in the radiation yield due to multiply repeated reflection from the curved surface. The output power of LED operating in a quasi-continuous wave mode was 30 μW at a current of 200 mA and that in a pulse mode was 0.6 mW at a current pulse amplitude of 2 A.

High-power InAs/InAsSbP heterostructure leds for methane spectroscopy (λ ≈ 3.3 μm)

Two designs of light-emitting diodes (LEDs) based on InAsSbP/InAs/InAsSbP double hetero-structures grown by metal-organic vapor phase epitaxy on p− and n-InAs substrates have been studied. The current-voltage and electroluminescence characteristics of the LEDs are analyzed. It is shown that the LED design with a light-emitting crystal (chip) mounted with the epitaxial layer down on the LED case and emission extracted through the n-InAs substrate provides better heat removal. As a result, the spectral characteristics remain stable at increased injection currents and the quantum efficiency of radiative recombination is higher. The internal quantum efficiency of light-em itting structures with an emission wavelength λ = 3.3–3.4 μm is as high as 22.3%. The optical emission power of the LEDs is 140 μW at a current of 1 A in the quasi-continuous mode and reaches a value of 5.5 mW at a current of 9 A in the pulsed mode.

Photodiodes based on InAs/InAsSb/InAsSbP heterostructures with quantum efficiency increased by changing directions of reflected light fluxes

It is shown, using the example of InAs/InAsSb/InAsSbP heterostructures, that the formation of a curvilinear reflecting surface consisting of hemispherical etch pits on the rear side of a photodiode chip leads to an increase in the quantum efficiency of photodiodes by a factor of 1.5–1.7 in the entire mid-IR wave-length interval studied (λ = 3–5 μm). For the obtained photodiodes with a cutoff wavelength of 4.8 μm, a photosensitive area of 0.1 mm2, and a chip area of 0.9 mm2, a monochromatic responsivity at λ = 4.0 μm reached 0.6 A/W, while a dark current at a reverse bias voltage of 0.2 V was within 4–6 A/cm2.

High-speed photodiodes for the mid-infrared spectral region 1.2–2.4 μm based on GaSb/GaInAsSb/GaAlAsSb heterostructures with a transmission band of 2–5 GHz

High-speed p-i-n photodiodes for the spectral range of 1.2–2.4 μm are fabricated for the first time based on a GaAs/GaInAsSb/GaAlAsSb heterostructure with separated sensitive-(50 μm in diameter) and contact mesas, which are connected by a bridge front contact. The use of an unconventional design for the contact mesa with a Si3N4 insulating sublayer 0.3 μm thick under the metal contact made it possible to lower both the intrinsic photodiode capacitance and the reverse dark currents. The photodiodes have a low intrinsic capacitance of 3–5 pF at zero bias and 0.8–1.5 pF at a reverse bias of 3.0 V. The photodiode operating speed, which is determined by the time of increasing the photoresponse pulse to a level of 0.1–0.9, is 50–100 ps. The transmission band of the photodiodes reaches 2–5 GHz. The photodiodes are characterized by low reverse dark currents Id = 200–1500 nA with a reverse bias of U = −(0.5–3.0) V, a high current monochromatic sensitivity of Ri = 1.10–1.15 A/W, and a detectability of D*(λmax, 1000, 1) = 0.9 × 1011 W−1 cm Hz1/2 at wavelengths of 2.0–2.2 μm.

Room-temperature photodiodes based on InAs/InAs0.88Sb0.12/InAsSbP heterostructures for extended (1.5–4.8 μm) spectral range

Photodiodes with a photosensitive area of 0.45 × 0.45 mm2 operating at room temperature in a wavelength range bounded by 4.9 μm have been created on the basis of InAs/InAs0.94Sb0.06/InAsSbP/InAs0.88Sb0.12/InAsSbP/InAs heterostructures grown by liquid phase epitaxy. A distinguishing feature of the proposed photodiodes is extended (λmax = 1.5–4.8 μm) spectral sensitivity range, in which the photodiode is characterized by a monochromatic responsivity of 0.5–0.8 A/W and a dark current density of 1.0–1.5 A/cm2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 20–100 Ω. The detection ability of photodiodes in the region of maximum sensitivity reaches (1–2) × 108 cm Hz1/2 W−1.

Mode synchronization in a laser with coupled disk cavities

Lasers operating on whispering gallery modes (WGMs) and emitting in the mid-IR wavelength range (2.2–2.4 µm) have been created on the basis of coupled semiconductor disk cavities with half-ring contacts. It is established that a separate connection of half-ring contacts of the WGM laser corresponds to a multimode character of radiation, while the connection of all (four) contacts leads to lasing in a single-mode regime. Possible mechanisms of mode synchronization in the proposed WGM lasers are discussed.

Increasing Output Power of LEDs (λ = 1.7-2.4 μm) by Changing Directions of Reflected Light Fluxes in GaSb/GaInAsSb/GaAlAsSb Heterostructures

It is demonstrated, using the example of light-emitting diodes (LEDs) based n-GaSb/n-GaIn-AsSb/p-GaAlAsSb heterostructures, that the formation of a curvilinear reflecting surface consisting of hemispherical etch pits on the rear side of an LED chip leads to an increase in the output radiation power by a factor of 1.9–2 in the entire wavelength interval studied (λ = 1.7–2.4 μm) as compared to the LED chip design with a continuous absorbing ohmic contact. This increase in the LED efficiency is related to a change in the directions of reflected light fluxes upon reflection from the hemispherical etch pits.