S. S. Kizhaev

Broken-gap heterojunction in the p-GaSb-n-InAs1−x Sbx(0≤x≤0.18) system

Epitaxial InAs1−xSbx layers with the Sb content 0≤x≤0.18 were grown by metalorganic vapor phase epitaxy (MOVPE) on p-GaSb and n-InAs substrates. The photoluminescence (PL) spectra of the heterostructures were measured at T=77 K. The experimental PL data were used to study variation of the bandgap as a function of the InAsSb solid solution composition. The energy difference between the GaSb valence band top and the InAs0.82Sb0.18 conduction band bottom was calculated. It was established that GaSb/InAs1− xSbx with 0≤x≤0.18 represents a broken-gap heterojunction of type II.

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.

LEDs (λmax = 3.6 μm) with cone-shaped light-emitting surfaces

A series of light-emitting diodes (LEDs) operating at λmax = 3.6 μm are created using cone-shaped mesas with heights of 10–130 μm and concave side surfaces. The dependence of the efficiency of room-temperature (T = 298 K) emission on the mesa height at various injection currents has been studied. The character of the observed dependence agrees with the results of theoretical calculations. The output radiation power of LEDs with the maximum mesa height (130 μm) at a pumping current of 220 mA amounts to 53 μW, which is 1.5 times higher than the power of LEDs with a mesa height of 10 μm.

Type II heterostructures with InSb quantum dots inserted into p-n InAs(Sb,P) junction

We report on study of electrical and optical properties of type II heterostructures with InSb quantum dots (QDs) inserter into the InAs-based p-n junction made by LPE-MOVPE combine method. InSb QDs were grown on an InAs(100) substrate by LPE. Overgrowth on the surface with the self-assembled InSb QD arrays was performed by MOVPE using capping layers based on binary InAs and quaternary InAsSb solid solutions. High-resolution cross-sectional image of the InSb QDs buried into the InAs(Sb,P) matrix was obtained for the first time by transmission electron microscopy. Structural parameters of the InSb QDs such as size, shape and internal strain were demonstrated and discussed. The uniform small QDs with high density (>1010 cm-2) with dimensions of 3 nm in height and 14 nm in diameter were found to be self-assembled and dislocation-free without any extended defects, whereas the low-density large QDs (108 cm-2) with dimensions of 10 nm in height and 50 nm in diameter were relaxed and demonstrated interface strain with the InAs substrate. I-V characteristics of the mesa-diode heterostructures with the InSb QDs inserted into InAs p-n junction were studied at the wide temperature range T=77-300 K. Intense positive and negative electroluminescence for both n-InAs/p- InAs and n-InAs/InSb-QDs/p-InAs heterostructures was found in the spectral range 3-4 μm. Evolution of the spectra in dependence on applied external bias (forward and reverse) were observed at 77 K and 300 K.

InAs/InAsSbP light-emitting structures grown by gas-phase epitaxy

Using the metal-organic chemical vapor decomposition technique, light-emitting diodes based on InAs/InAsSbP double heterostructures emitting in a wavelength range around 3.3 µm have been fabricated. The external quantum yield of the diodes is 0.7%. In laser diodes, stimulated emission at a wavelength of 3.04 µm has been obtained at T=77 K.

Long-wavelength light-emitting diodes (λ=3.4–3.9 µm) based on InAsSb/InAs heterostructures grown by vapor-phase epitaxy

InAs/InAs0.93Sb0.07/InAs heterostructures were grown by metal-organic vapor-phase epitaxy in a horizontal reactor at atmospheric pressure. Based on the obtained structures, light-emitting diodes operating at λ=3.45 µm (T=77 K) and λ=3.95 µm (T=300 K) were fabricated. The room-temperature quantum efficiency of light-emitting diodes was 0.12%.

Electrical and electroluminescent properties of InAsSb-Based LEDs (λ = 3.85–3.95 μm) in the temperature interval 20–200°C

The temperature dependences of the electrical and electroluminescent properties of InAsSbP/InAsSb/InAsSbP heterostructure LEDs (λ ≈ 3.8−4.0 μm) are studied in the temperature interval 20–200°C. It is shown that the radiation power decreases with increasing temperature in a superexponential manner and that this decrease is associated primarily with a rise in the rate of Auger recombination. The position of the maximum in the radiation spectrum varies with temperature nonmonotonically, since radiative recombination is observed both in the active region and in the wide-gap layer. At room temperature, current through the heterostructure is tunneling current irrespective of the applied voltage polarity. As the temperature rises, either the thermal emission of charge carriers appears (direct bias) or the diffusion current becomes significant (reverse bias).

InSb quantum dots and quantum rings in a narrow-gap InAsSbP matrix

We report a study of InSb quantum dots and quantum rings grown on InAs(100) substrate by LPE-MOVPE combine method. Characterization of InSb/InAs(Sb,P) quantum dots was performed using atomic force microscopy and transmission electron microscopy. The bimodal growth of uncapped InSb quantum dots was observed in the temperature range T=420-450 °C. The low-density (5×108 cm-2) large quantum dots with dimensions of 12-14 nm in height and 45-50 nm in diameter are appeared at 445 °C, whereas high-density (1×1010 cm-2) dislocation-free small quantum dots with dimensions of 3-5 nm in height and 11-13 nm in diameter were obtained at 430 °C. Capping of the InSb quantum dots by binary InAs or InAsSbP epilayers lattice-matched with InAs substrate was performed using MOVPE method. Tunnel-related behavior in a forward curve of I-V characteristics was observed in heterostructures with buried InSb quantum dots inserted in InAs p-n junction. Evolution of electroluminescence spectra on driving current at negative bias and suppression of negative luminescence from buried InSb/InAs quantum dots were found out in the spectral range 3-4 μm at 300 K. Deposition from the InSb melt over the InAsSb0.05P0.10 capping layer resulted in the formation of InSb quantum rings with outer and inner diameters about 20-30 nm and 15-18 nm respectively. Surface density of the quantum rings of 2.6×1010 cm-2 was reached at 430 °C.

Characterization of light-emitting diodes based on InAsSbP/InAsSb structures grown by metal-organic vapor-phase epitaxy

Light-emitting diodes for the wavelength range λ=3.3–4.5 µm were fabricated on the basis of InAsSbP/InAsSb heterostructures grown by metal-organic vapor-phase epitaxy. The use of vapor-phase epitaxy made it possible to appreciably increase the phosphorus content in barrier layers (up to 50%) in comparison with that attainable in the case of liquid-phase epitaxy; correspondingly, it was possible to improve confinement of charge carriers in the active region of the structures. Photoluminescent properties of InAsSb layers, electroluminescent properties of light-emitting diodes, and dependences of the emission power on current were studied. Two types of light-emitting diodes were fabricated: (i) with extraction of emission through the substrate (type A) and (ii) with extraction of emission through the epitaxial layer (type B). The light-emitting diodes operating in the pulse mode (with a relative pulse duration of 20) had an emission power of 1.2 mW at room temperature.

LEDs Based on InAsSbP/InAsSb Heterostructures (λ = 4.7 μm) for Carbon Monoxide Detection

Light-emitting diodes (LEDs) operating in the 4.4–4.8-μm wavelength range have been developed for detecting the presence of carbon monoxide (CO) in air. The proposed LEDs are based on InAsSbP/InAsSb heterostructures with InAs0.85Sb0.15 active region, which were grown by metalorganic vapor-phase epitaxy. The electrolumuinescent properties of LEDs have been studied. The output power of LED operating in a pulsed mode reaches 50 μW at a current pulse amplitude of 2 A, and that in a quasi-continuous wave mode is 1 μW at a current of 200 mA. The absorption of LED radiation in a gaseous medium containing 10% CO has been studied. The proposed LEDs can be used to simultaneously detect both CO2 (absorbing at λ = 4.3 μm) and CO (λ = 4.67 μm).