InAsSbP double-heterostructure lasers for the spectral range 2.7–3.0 µm (T=77 K)

We have produced, by using liquid-phase epitaxy, 2.7 to 3.0-μm lasers based on InAsSbP double-heterostructures with different phosphorus contents in the active and wide-gap regions. The lasers possess threshold current density ∼0.8 kA/cm² at 77 K and operate in the pulsed mode up to ∼124 K with maximum threshold current density 10–12 kA/cm². The lasers have a low series resistance ∼0.45 Ω. Fiz. Tekh. Poluprovodn. 32, 241–244 (February 1998)     

Light-emitting diodes based on GaSb alloys for the 1.6–4.4 μm mid-infrared spectral range

The available publications concerned with fabrication and study of light-emitting diodes (LEDs) intended for operation in the 1.6–4.4 μm spectral range; based on GaSb substrates; and grown by liquid-phase epitaxy, which makes it possible to form fairly thick layers lattice-matched to GaSb, are reviewed. In these studies, the active region consists of the GaInAsSb compound in LEDs for the spectral ranges 1.8–2.4 and 3.4–4.4 μm and the AlGaAsSb compound for the spectral region 1.6–1.8 μm. The wide-gap AlGaAsSb confining layers contain up to 64% of Al, which is an unprecedentedly high content for liquid-phase epitaxy. Asymmetric (GaSb/GaInAsSb/AlGaAsSb) and symmetric (AlGaAsSb/GaInAsSb/AlGaAsSb) heterostructures have been fabricated and studied. Various types of designs that make it possible to improve the yield of radiation generated in the active region have been developed. The measured external quantum yield of emission is as high as 6.0% at 300 K for the LEDs operating at the wavelengths 1.9–2.2 μm. A pulsed optical-radiation power of 7 mW at a current of 300 mA with a duty factor of 0.5 and 190 mW at a current of 1.4 A with a duty factor of 0.005 have been obtained. The external quantum emission yield of ～1% has been obtained for LEDs that emit in the spectral range 3.4–4.4 μm; this yield exceeds that obtained for the known InAsSb/InAsSbP heterostructure grown on an InAs substrate by a factor of 3. The measured lifetime of minority charge carriers (5–0 ns) is close to the theoretical lifetime if only the radiative recombination and impact CHCC bulk recombination are taken into account. The impact recombination is prevalent at temperatures higher than 200 K for LEDs operating in the spectral range 3.4–4.4 μm and at temperatures higher than 300 K for LEDs operating in the spectral range 1.6–2.4 μm.     

Transformation of a short-wavelength emission band of a double-charged intrinsic acceptor into a long-wavelength band in GaSb-based LEDs

GaSb-based crystals shaped like a stepped pyramid with smoothed steps are obtained. The crystals are intended for the fabrication of light-emitting diodes in which the short-wavelength emission band of a double-charged intrinsic acceptor is transformed into the long-wavelength band without loss in the amount of photons emitted. It is shown experimentally and theoretically that an increase in the ratio of the area of the light-emitting diode crystal to its volume increases the external quantum yield of photons. A yield of 5.1% for the intrinsic acceptor in GaSb is attained.     

LEDs (λ<Subscript>max</Subscript> = 3.6 μm) with cone-shaped light-emitting surfaces

A series of light-emitting diodes (LEDs) operating at λ_max = 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.     

Influence of pumping uniformity on current tuning of the emission wavelength of InAsSb/InAsSbP diode lasers

An investigation was made of continuous tuning of the emission wavelength in two types of InAsSb/InAsSbP diode heterolasers: three-layer structures with combined electrical and optical confinement and five-layer structures with separate confinement. In three-layer structures the emission wavelength initially decreases by 2–4 Å with increasing current and then increases by 10–15 Å. In five-layer structures the emission wavelength mainly decreases. This difference is attributed to the better flow of carriers in the bulk of the active region in five-layer structures as compared with three-layer ones. Pis’ma Zh. Tekh. Fiz. 24, 77–84 (March 26, 1998)     

Simultaneous interface and interband lasing in InAs/InAsSbP heterostructures grown by metalorganic vapor phase epitaxy

Coherent radiation sources have been manufactured based on double heterostructures of the InAs/InAsSbP type grown by metalorganic vapor-phase epitaxy. The mode composition of the lasing spectrum is determined by simultaneous induced recombination at the heteroboundary and in the bulk of the active region, as well as nongenerated modes with intermediate frequencies. Additional optical losses at the intermediate modes decrease the slope of the laser intensity dependence on the current.     

Short-wavelength current tuning of InAsSb/InAsSbP heterostructure lasers caused by an injection nonuniformity

A reduction in the emission wavelength in the preferred mode of InAsSbP/InAsSb/InAsSbP heterostructure lasers by 50Å is observed when the current is raised from 1.8 to 5 times the threshold with dc and pulsed power. A comparison of the spectral and spatial distributions of the output as functions of current shows that this short-wavelength tuning is caused by a change in the distribution of the nonequilibrium charge carrier concentration over the strip width as the current is varied. This effect is modeled mathematically, taking into account the increase in the injection density and the drop in the output intensity from the middle to the sides of the waveguide. The results of the model calculation are in good agreement with experiment.     

InAsSb/InAsSbP heterostructure lasers with a large range of current tuning of the lasing frequency

The lasing spectra and the shift in the position of the modes in the current range (1–5)I _th with various methods of pumping the nonequilibrium charge carriers are analyzed. It is shown that the pumping method does not influence the character of the tuning of the radiation line. The large short-wavelength tuning range (up to 50 Å) is due not to the heating of the crystal lattice in the active-region material but rather the nonuniform nonequilibrium charge-carrier density distribution over the width of the stripe. Pis’ma Zh. Tekh. Fiz. 25, 17–23 (October 12, 1999)     

High-efficiency LEDs based on GaInAsSb solid solutions with reduced arsenic content in the active region

Light-emitting diodes (LEDs) with the active region based on Ga_{1− x} In_xAs_ySb1−y solid solutions are obtained on GaSb substrates. The active region has a composition close to the domain of immiscibility (x = 0.24) and a reduced arsenic content (y = 0.16). The diode structures exhibit a high density of misfit dislocations. Nevertheless, the room-temperature external quantum yield reaches a record-high level of 1.2% in the spectral band with a maximum wavelength of 2.42 μm. The maximum output radiation pulse power reaches 3.3 mW at a current of 600 mA. The emission is predominantly due to the interband transitions, which is evidence of a high degree of stoichiometry of the active region.     

Current-tunable lasers with a narrow emission line operating at 3.3 µm

Current-tunable diode lasers with narrow emission lines for laser spectroscopy in the 3.2–3.4 μm wavelength range are developed. The lasers, based on an InAsSb/InAsSbP double heterostructure, have a wide-stripe cavity. The wave number increases from 3030 to 3034 cm⁻¹ as the current is raised from 1.5 to 3 times the threshold value at 70 K, while the full width at half-maximum of the laser line decreases from 18 to 10 MHz. It is demonstrated that the linewidth is determined by fluctuations of the cavity resonance frequencies as a result of fluctuations in the concentration of nonequilibrium charge carriers. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 3, 2001, pp. 375–379. Original Russian Text Copyright ? 2001 by Imenkov, Kolchanova, Kubat, Moiseev, Civiš, Yakovlev.