Spontaneously forming periodic composition-modulated InGaAsP structures

InGaAsP epitaxial layers, which are obtained in the instability region on InP (001) and GaAs (001) substrates, are investigated by photoluminescence and transmission-electronmicroscopy methods. The results are discussed on the basis of the theory of spinodal decomposition of solid solutions. It is established experimentally that in certain temperature and composition ranges the solid solutions InGaAsP are a system of charged, alternating (in mutually perpendicular directions [100] and [010]) domains of a solid solution with two different compositions and different lattice constants. The domain structure is very clearly defined at the surface of the epitaxial film and becomes blurred in the film near the substrate. The data obtained very likely show spinodal decomposition of the solid solutions InGaAsP in the test samples. Fiz. Tekh. Poluprovodn. 33, 544–548 (May 1999)     

Epitaxial deposition of InGaAsP solid solutions in the miscibility gap

Liquid-phase epitaxy of InGaAsP solid solutions isoperiodic with (001)GaAs substrates was studied in the miscibility gap. At the initial stage of deposition (first 1–2 s), thin (up to 0.15 μm) planar layers of homogeneous InGaAsP solid solutions are formed. This is aided by pronounced supercooling of the melt (by 10–15°C) and the resulting high growth rates. In further stages, growth becomes slower and a natural nanoheterostructure starts to form owing to decomposition of the solid solution. The formation of a nanoheterostructure comprising domains of different compositions with different lattice constants is accompanied by the appearance of an undulating relief on the sample surface, with the undulation magnitude increasing as the layer grows. Under the technological conditions employed, the thickness of InGaAsP solid solution layers containing a nanoheterostructure is limited to 0.5 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 11, 2000, pp. 1307–1310. Original Russian Text Copyright ? 2000 by Vavilova, Kapitonov, Murashova, Tarasov.     

Spontaneously assembling periodic composition-modulated InGaAsP structures

It is established theoretically and experimentally that in certain temperature and composition ranges the solid solutions InGaAsP comprise a system of strained, alternating (in mutually perpendicular directions [100] and [010]) domains of a solid solution with two different compositions and different lattice constants. The domains are clearly seen at the surface of an epitaxial film and wash out into its depth in the direction of the substrate. The data obtained most likely show spinodal decomposition of InGaAsP solid solutions in the experimental samples. Fiz. Tekh. Poluprovodn. 33, 1108–1110 (September 1999)     

GaInAsSb/GaSb heterostructures grown in the spinodal decay region by liquid-phase epitaxy from Sb-enriched solution-melts

Nearly isoperiodic solitary Ga_1−x In_xAs_ySb_1−y /GaSb heterostructures, in which the composition of the solid solution should be found inside the region of spinodal decay (x⩽0.4), were grown by liquid-phase epitaxy from solution-melts enriched with antimony. On the basis of the results of a study of structural and luminescence properties of Ga_1−x In_xAs_ySb_1−y /GaSb heterostructures we have determined the main conditions ensuring reproducible growth of epitaxial layers, homogeneous in the composition of their solid solutions in the region where the existence of processes of spinodal and binodal decay have been theoretically predicted. It is shown that the magnitude and sign of the deformation which the layer undergoes during growth and also the thickness of the layer are the main factors influencing the properties of the growing GaInAsSb solid solutions in the spinodal-decay zone. Fiz. Tekh. Poluprovodn. 33, 1134–1136 (September 1999)     

Variation of the thickness and composition of lpe InGaAsP,InGaAs, and InP layers grown from a finite melt by the step-cooling technique

Constant composition InGaAsP and InGaAs epitaxial layers can be grown using the step-cooling technique. However, the requirement of a fixed growth temperature limits the maximum thickness that can be obtained. The thickness of InGaAsP (λ_g = 1.15 μm@#@), InGaAs (λ_g = 1.68 μm), and InP liquid phase epitaxial layers grown on (100) InP sub-strates by the step-cooling technique has been measured as a function of growth time. (λ_g is defined as the wave-length corresponding to the band gap of the epitaxial layer). For long growth times, the effect of the finite growth solution becomes important, and beyond a distinct growth time, constant composition growth can no longer be maintained. The maximum constant composition layer thick-ness obtainable is not severely restricted by the fixed growth temperature, and from the experimental results this maximum thickness can be estimated for any melt size.     

Deposition of InGaAsP alloys on GaAs by low pressure metalorganic vapor phase epitaxy: Theory and experiments

A combined thermodynamic-kinetic approach to the epitaxial deposition of InGaAsP alloys on GaAs substrates is presented. Good agreement with experimental group V solid phase incorporation has been found when neglecting the 2V₂ = V₄ (V = As,P) vapor phase reactions, while the group III solid phase composition is well described by simple mass-transport limited processes. InGaAsP materials, lattice matched to GaAs, have been grown in a wide composition range toward the ternary limit [In(0.49)Ga(0.51)P]. Furthermore, high quality InGaAsP/GaAs strained quantum wells with a bandgap below that of GaAs are realized for the first time.     

Analysis of electrical, threshold, and temperature characteristics of InGaAsP/InP double- heterojunction lasers

This paper presents an extensive study of the fundamental characteristics of InGaAsP/InP double-heterojunction (DH) lasers with a wavelength of 1.3 μm. The confinement properties of injected carriers in the quaternary active region, the electrical properties such as leakage current and diode current versus voltage, the threshold characteristics, and the threshold temperature characteristics are determined through an analysis of the heterojunction energy band structure. The threshold temperature characteristics and the carrier leakage from the active region into the confining layers are examined in detail. To clarify the dependence of carrier leakage on lasing wavelength in InGaAsP/InP DH lasers and to explain the difference between GaAlAs/GaAs DH and InGaAsP/InP DH lasers, the barrier heights required to effectively confine the injected carriers and the effective carrier masses in the active region are discussed. Various possible explanations for the observed threshold temperature characteristics are considered.     

Infrared reflection spectra of multilayer epitaxial heterostructures with embedded InAs and GaAs layers

The effect of the thickness of embedded InAs and GaAs layers on the infrared reflection spectra of lattice vibrations for AlInAs/InAs/AlInAs, InGaAs/GaAs/InGaAs, and AlInAs/InGaAs/GaAs/InGaAs/AlInAs multilayer epitaxial heterostructures grown by MOC hydride epitaxy on InP (100) substrates is studied. Relative stresses emerging in the layers surrounding the embedded layers with variation in the number of monolayers from which the quantum dots are formed and with variation the thickness of the layers themselves surrounding the embedded layers are evaluated.     

Atomic layer epitaxy of InP

In this work we will discuss the growth conditions for ALE of InP. Growth experiments were carried out in a LP-MOCVD system with a fast switch gas manifold. InP layers were deposited by pulsing TMIn and PH₃, using Argon as carrier gas. A self limiting growth rate at 1 ML/cycle has been obtained with a substrate temperature as low as 320-360° C. InP epitaxial layers were grown on GaAs and InP substrates, and on GaInAs(P) layers previously deposited by conventional MOCVD. Selective area epitaxy on InP using a Si₃N₄ mask was also demonstrated. Results of this study are very encouraging for hybrid MOCVD/ALE growth of In-based compounds.     

Optical and structural properties of ingaasp miscibility-gap solid solutions grown by MOVPE on GaAs(001) substrates

Optical and structural properties of InGaAsP solid solutions grown by MOVPE at 600°C on GaAs(001) substrates are studied. The photoluminescence spectra of InGaAsP solid solutions with a composition corresponding to the miscibility gap contain a main band and an additional auxiliary band. It is established that both bands are related to band-to-band radiative transitions; i. e., the studied layer includes two solid solutions with different compositions and different band gaps. It is shown that the observed high-energy shift of the additional band with an increasing level of excitation is governed by the nanometer size of domains in the corresponding solid solution. This conclusion is consistent with the results of TEM study, which revealed the presence of a periodic structure comprised of alternating domains with different compositions. This structure of alternating domains extends along the [100] and [010] directions with a characteristic period of 10 nm.     

Very low threshold InGaAsP mesa laser

Very low threshold currents InGaAsP/InP terrace mesa (T-ME) lasers with an unpassivated surface have been fabricated on semi-insulating (SI) InP substrates. Fabrication of the lasers involves a single-step liquid phase epitaxial (LPE) growth and a simple etching process. Lasers operating in the fundamental transverse mode with threshold currents as low as 6.3 mA (for a cavity length of 250 μm) have been obtained. Comparison between the unpassivated lasers and those passivated using the mass transport technique is described.     

Lattice constant,bandgap, thickness,and surface morphology of InGaAsP-InP layers grown by step-cooling,equilibrium-cooling,supercooling and two-phase-solution growth techniques

Constant composition InGaAsP epitaxial layers can be grown on (100) InP substrates at a constant temperature using the diffusion-limited step-cooling growth technique, and in general, compositionally graded layers result when the diffusion-limited equilibrium-cooling, supercooling, and two-phase-solution growth techniques are used. The lattice constant and energy gap of the epitaxial layers grown using the step-cooling technique are nearly independent of small variations of X _p ^l and the amount of step cooling, but are dependent on growth temperature. The dependence of lattice constant and energy gap of the epitaxial layers on X _Ga ^l and X _As ^l has been determined for the step-cooling and supercool ing techniques.     

InAs/InGaSb photodetectors grown on GaAs bonded substrates

The results of wafer fusion between GaAs and InP followed by transfer of an InGaAs film from the InP to GaAs substrate are presented in this paper. This technique of film transfer allowed the subsequent growth of epitaxial materials with approximately 7% lattice mismatch. Type-II InAs/GaInSb superlattices photodetectors of different designs have been grown by molecular beam epitaxy (MBE) on the alternative InGaAs/GaAs substrate and on standard GaSb substrates. Comparison between photodetectors grown on the two different substrates with nearly identical superlattice periods showed a shift in the cut-off wavelength. The superlattices grown on the alternative substrates were found to have uniform layers, with broader x-ray linewidths than superlattices grown on GaSb substrates.     

Characterization of (111) Gaas and (111) InP substrates and homoepitaxial layers by divergent x-ray beam diffraction

The back-reflection diffraction of a divergent x-ray beam has been studied for the characterization of (111) GaAs and (111) InP substrates and homoepitaxial layers with different states of surface perfection. Diffraction conditions for generating back-reflection pseudo-Kossel patterns from (111) GaAs and (111) InP are presented. Mechanical polishing was observed to produce x-ray diffraction line broadening. Uneven line broadening was found to be produced by an inhomogeneous distribution of dislocations. The diffraction angles for pseudo-Kossel lines were influenced by subgrain tilting in epitaxial, LPE-grown layers. A close relationship between diffraction line profiles and surface morphology of the epitaxial layer was demonstrated with interference-contrast optical microscopy.     

InGaAsP/InP photodiodes: Microplasma-limited avalanche multiplication at 1-1.3-µm wavelength

Photodiodes for use in the1-1.3-mum wavelength region have been fabricated from double-heterostructure InGaAsP/InP wafers grown by liquid-phase epitaxy (LPE). The measured avalanche multiplication in mesa-configuration devices was limited to values of 10 or less. The results of careful measurement of the photoresponse, quantum efficiency, and reverse-biasI-Vcharacteristics suggest that the gain is limited by microplasma breakdown. The density of microplasmas was estimated to be about 10⁶cm^-2, approximately equal to the etch pit density of the InP substrates used in growth of the epitaxial layers.     

Saturation of light-current characteristics of high-power laser diodes (λ = 1.0–1.8 μm) under pulse operation

Spectral and light-current characteristics of separate-confinement lasers that are based on InAl-GaAs/InP and InGaAsP/InP alloys and emit in the wavelength range of 1.5–1.8 μm are studied at high excitation levels (up to 80 kA/cm²) in pulse operation (100 ns, 10 kHz). It is shown that the peak intensity in the stimulated-emission spectrum saturates as the pump current is increased. Further increase in the emitted power is attained owing to the emission-spectrum broadening to shorter wavelengths, similar to lasers on the GaAs substrates (λ = 1.04 μm). It is established experimentally that the broadening of the stimulated-emission spectrum to shorter wavelengths is caused by an increase in the threshold current and by an increase in the charge-carrier concentration in the active region. This concentration increases by a factor of 6–7 beyond the lasing threshold and can be as high as 10¹⁹ cm^?3 in pulse operation. It is shown that saturation of the light-current characteristics in pulse operation takes place in the InAlGaAs/InP and InGaAsP/InP lasers as the pump current is increased. It is shown experimentally that there is a correlation between saturation of the light-current characteristic and an increase in the threshold current in the active region. An increase in the charge-carrier concentration and gradual filling of the active region and waveguide layers with electrons are observed as the pump current is increased; stimulated emission from the waveguide is observed at high pump currents.     

MOVPE-grown 1.5 µm distributed feedback lasers on corrugated InP substrates

A single-step low-pressure metalorganic vapor phase epitaxy (MOVPE) was applied to the fabrication of 1.5 μm InGaAsP/InP distributed feedback laser diodes on corrugated InP substrates, accompanied by LPE for buried heterostructure formation. High probability of single longitudinal mode operation was obtained due to the uniformity of the active layer thickness. A typical threshold current was 35 mA with both facets cleaved. A maximum output power of up to 27 mW was also obtained under single longitudinal mode operation with anti-reflective/cleaved facet configuration. The laser diode had high spectral stability under high-frequency direct modulation of 1.4 GHz. Results of initial aging tests (APC of 5 mW at 25°C for longer than 3800 h) have shown no degradation in driving currents. It is found that low-pressure MOVPE is favorable for epitaxial growth on corrugated substrates.     

Metalorganic InP and Inx Ga1-x,Asy P1-y,on InP epitaxy at atmospheric pressure

We present a procedure for the MOVPE of InP as simple as the one currently used for GaAs. InP and InGaAsP alloys are grown on InP substrates using trimethy1indium (TMI), phosphine, trimethylgallium (TMG) and arsine. The choice of carrier gas is important ; a mixture of hydrogen and nitrogen allowed us to grow uniform layers over large areas at atmospheric pressure, without pyrolizing the phosphine or separating the input reactants. Preliminary characterization results are presented. Most information contained in this paper was presented at the 1983 Electron Materials Conference as paper Cl.     

High-power diode lasers (λ = 1.7–1.8 µm) based on asymmetric quantum-well separate-confinement InGaAsP/InP heterostructures

Advantages of the concept of high-powered semiconductor nanoheterostructure lasers for the spectral range 1700–1800 nm, grown by MOCVD in the InGaAsP/InP solid solution system, have been experimentally demonstrated. It has been found that using an expanded waveguide enables reduction to 2 cm^?1 of the internal optical loss in quantum-well asymmetric separate-confinement double InGaAsP/InP heterostructures emitting at a wavelength of 1.76 µm. The heterostructures developed have been used to create multimode lasers with a room-temperature CW output power of 2.5 W in an aperture of 100 µm. It is shown that use of highly stressed quantum-well InGaAs layers as the active region makes it possible to obtain characteristic temperatures T ₀ = 50–60 K.     

Terahertz-radiation generation in low-temperature InGaAs epitaxial films on (100) and (411) InP substrates

The spectrum and waveforms of broadband terahertz-radiation pulses generated by low-temperature In_0.53Ga_0.47As epitaxial films under femtosecond laser pumping are investigated by terahertz time-resolved spectroscopy. The In_0.53Ga_0.47As films are fabricated by molecular-beam epitaxy at a temperature of 200°C under different arsenic pressures on (100)-oriented InP substrates and, for the first time, on (411)A InP substrates. The surface morphology of the samples is studied by atomic-force microscopy and the structural quality is established by high-resolution X-ray diffraction analysis. It is found that the amplitude of terahertz radiation from the LT-InGaAs layers on the (411)A InP substrates exceeds that from similar layers formed on the (100) InP substrates by a factor of 3–5.