K. V. Kalinina

Superlinear electroluminescence due to impact ionization in GaSb-based heterostructures with deep Al(As)Sb/InAsSb/Al(As)Sb quantum wells

We report on the observation of superlinear electroluminescence (EL) in nanoheterostructures based on GaSb with a deep narrow Al(As)Sb/InAsSb/Al(As)Sb quantum well (QW) in the active region, grown by metal organic vapor phase epitaxy. Electroluminescence spectra for different driving currents were measured at temperatures of 77 and 300 K. It is shown that such structure exhibits superlinear dependence of optical power on the drive current and its increase of 2–3 times in the current range 50–200 mA. This occurs due to impact ionization in the Al(As)Sb/InAsSb quantum well in which a large band offset at the interface ΔEC = 1.27 eV exceeds ionization threshold energy for electrons in the narrow-gap well. Calculation of the size quantization energy levels is presented, and possible cases of impact ionization, depending on the band offset ΔEC at the interface and on the quantum well width, are considered. This effect can be used to increase quantum efficiency and optical power of light emitting devices (laser...

Superlinear electroluminescence in GaSb-based heterostructures with high potential barriers

The electroluminescence in isotype and anisotype light-emitting diode heterostructures grown by the method of liquid-phase epitaxy with large conduction-band offset ΔEc at the heterointerface between a narrow-band active region and a wide-band layer is studied. Two types of electroluminescence peaks are observed in the range of photon energies 0.28–0.74 eV at temperatures T = 300 and 77 K; in this case, a super-linear increase in the intensity and optical power of emission by a factor of 1.5–2 is observed in the range of pump currents 20–220 mA. This effect is attributed to the formation of additional electron-hole pairs as a result of impact ionization by hot electrons heated as a result of the band offset ΔEc in the conduction band at the n-AlGaAsSb/n-InGaAsSb and n-GaSb/n-InGaAsSb heteroboundaries. This effect can be used to increase the quantum efficiency of semiconductor emitters (light-emitting diodes, lasers) in the mid-infrared region.

Portable optical water-and-oil analyzer based on a mid-IR (1.6–2.4 μm) optron consisting of an LED array and a wideband photodiode

An optical method for measuring the water and oil content using mid-IR (1.6–2.4 μm) LEDs and a wideband photodiode is suggested for the first time. This method is developed based on the absorption spectra of pure water, dewatered oil, and water—oil emulsions (cut oil) with different content of water and uses 10 types of LEDs in the spectral range 1.6–2.4 μm. It is shown that pure water heavily absorbs the LED radiation in the spectral range 1.85–2.05 μm, oil absorbs in the range 1.67–1.87 μm, and the LED radiation with a maximum at 2.20 μm is equally weakly absorbed by water and oil. An optical cell of the water-and-oil analyzer is designed on the basis of a three-element diode array with radiation maxima at 1.65 (detection of oil), 1.94 (detection of water), and 2.2 μm (reference signal) wideband photodiode covering the spectral range 1.3–2.4 μm. A calibration curve is derived that represents the dependence of the water concentration in oil on the amplitude of the reduced signal obtained by processing three signals from the LEDs. This optical method of measuring the water content in oil underlies a portable analyzer making possible online measurements directly in an oil well.

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 n-GaSb/n-GaInAsSb/p-AlGaAsSb heterostructures grown using rare-earth elements for the 1.1–2.4 μm spectral range

Photodiodes sensitive in the wavelength range of 1.1–2.4 μm have been created based on n-GaSb/n-GaInAsSb/p-AlGaAsSb heterostructures with a narrow-gap n-GaInAsSb layer (Eg ≅ 0.5 eV) grown in the presence of a rare-earth element (holmium). The electron concentration in the narrow-gap layer is n = 1 × 1016 cm−3, which is about one-fourth of that in an analogous structure grown without the rare-earth element. The proposed structure is characterized by increased quantum efficiency and response speed.

Frequency-tuned semiconductor whispering-gallery-mode laser (λ = 2.35 µm) operating at room temperature

Frequency tuning in a whispering gallery mode (WGM) semiconductor laser (λ = 2.35 µm) with a sector (half-disk) cavity has been studied. Pumping by current pulses with a duration of up to 1.2 µs is accompanied by smooth tuning of the main WGM toward longer wavelengths by 30 Å at room temperature, which is 1.4 times the intermode distance.

Continuous-wave disk WGM lasers (λ = 3.0 μm) based on InAs/InAsSbP heterostructures

IR semiconductor WGM lasers operating in the continuous-wave (CW) mode at a wavelength of 3.04 μm have been fabricated by metal-organic vapor-phase epitaxy on the basis of InAs/InAsSbP heterostructures. Their emission spectra were studied in the temperature range from 77 to 125 K. The lasers operating in the CW mode have a threshold current of 25 mA at a temperature of 77 K. The WGM lasers also work in the pulsed mode up to 125 K. The dynamic range of operation for the disk lasers is substantially extended to currents exceeding the threshold current by a factor of 200.

High-temperature luminescence in an n-GaSb/n-InGaAsSb/p-AlGaAsSb light-emitting heterostructure with a high potential barrier

The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔEc = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290–480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290–345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region.

Low-noise photodiodes based on GaSb/GaInAsSb/AlGaAsSb double heterostructures for the 1–4.8 μm spectral range

Photodiode heterostructures n-GaSb/n-GaInAsSb/p-AlGaAsSb with a red cutoff at 4.8 μm are studied. It is shown that making higher the content of In and Al in the narrow-gap and wide-gap layers, respectively, improves the photoelectric parameters of a structure via elimination of the tunnel leakage across the n-GaInAsSb/p-AlGaAsSb junction. A detectivity Dλ* = 1.1 × 109 cm Hz1/2 W−1 at room temperature was obtained.

High-temperature luminescence in light-emitting heterostructures with a high potential barriers based on GaSb

The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔEc = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence spectrum. In the entire temperature range under study, T = 290 – 480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated on the large the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the electroluminescence intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290 – 345 K, and a linear increase is observed at T < 345 K. Theoretical calculations have shown that this behavior of the temperature dependence of the optical power caused by competition between the radiative recombination, thermionic emission and Auger recombination.