InGaAsP photodiodes

InGaAsP photodiodes are finding wide applications in long wavelength fiber-optical communication systems. Particular requirements that these detectors must satisfy include low capacitance, high speed, and low noise capabilities. High-purity InGaAsP materials are necessary to meet these requirements. Low-noise detectors also require low reverse dark current. For avalanche diode applications, the electron and hole impact ionization coefficients are important parameters. In this paper we review recent work including LPE growth of high-purity InP and InGaAs, studies of the tunneling component of the dark current, and measurements of the impact ionization coefficients and excess noise factor in InGaAsP photodiodes.     

Recent advances in the performance and reliability of InGaAsP LED's for lightwave communication systems

High radiance LED's are being exploited in lightwave applications where their low cost, wide temperature range of operation, and outstanding reliability outweigh the power and modulation advantages of injection laser diodes. Development activity and commercial offerings of LED's have been rapidly moving toward InGaAsP LED's to take advantage of the low attenuation and chromatic dispersion minimum at the 1.3-µm emission wavelength. This paper reviews recent advances in the performance, reliability, and system application of InGaAsP LED's.     

Epitaxial growth, electronic properties, and photocathode applications of strained pseudomorphic InGaAsP/GaAs layers

The results of experimental and theoretical investigations directed toward the development of highly efficient sources of spin-polarized electrons are reported. The sources are based on heteroepitaxial elastically strained films of the quaternary InGaAsP solid solution grown by liquid-phase epitaxy on GaAs substrates. The InGaAsP films synthesized were 0.1–0.2 μm thick with the band gap being within the range of 1.4–1.9 eV and having elastic strains as high as 1%. This provided splitting of the valence band top by 40–60 meV and a degree of the spin polarization P of the electrons photoemitted as high as 80%. The films have a high quantum yield of photoemission Y upon activating to the negative electron affinity state due to the adsorption of Cs and O. Record values for the effective figure of merit P ² Y are achieved. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 9, 2001, pp. 1102–1110. Original Russian Text Copyright ? 2001 by Alperovich, Bolkhovityanov, Chikichev, Paulish, Terekhov, Yaroshevich.     

Intermixing of InP-based multiple quantum wells for integrated optoelectronic devices

The intermixing characteristics of three widely used combinations of InP-based quantum wells (QW) are investigated using the impurity-free vacancy disordering (IFVD) technique. We demonstrate that the bandgap energy shift is highly dependent on the concentration gradient of the as-grown wells and barriers, as well as the thickness of the well, with thinner wells more susceptible to interdiffusion at the interface between the barrier and well. According to our results, the InGaAsP/InGaAsP and InGaAs/InP are well suited for applications requiring a wide range of bandgap values within the same wafer. In the case of the InGaAs/InGaAsP system, its use is limited due to the significant broadening of the photoluminescence spectrum that was observed. The effect of the top InGaAs layer over the InP cladding is also investigated, which leads to a simple way to obtain three different bandgaps in a single intermixing step.     

High power single-mode (λ=1.3–1.6 μm) laser diodes based on quantum well InGaAsP/InP heterostructures

The possibility of achieving maximal optical output power in the single-mode lasing for mesa-stripe laser diodes fabricated on the basis of InGaAsP/InP quantum-well heterostructures with separate confinement have been studied both experimentally and theoretically. The basic condition for the single-mode lasing of laser diodes in a wide range of driving currents is shown to be the precise choice of the effective refractive index Δn _L discontinuity in the plane parallel to the p-n junction. A InGaAsP/InP separate confinement heterostructure with a step waveguide, with a threshold current density of 180 A/cm² and an internal quantum efficiency of stimulated emission of 93–99%, has been manufactured via the MOCVD method. The optimization of the mesa-stripe diode design for the developed InGaAsP/InP heterostructure is carried out with the aim of achieving maximal optical output power in the case of single-mode lasing. An output power of 185 mW is attained in the laser diode with the mesa-stripe width W=4.5 μm (λ=1480 nm). The maximal continuous output power was as high as 300 mW. The full width at half-maximum (FWHM) of the lateral far-field pattern increased by 1° relative to the threshold value.     

Time-Resolved Linewidth Enhancement Factors in Quantum Dot and Higher-Dimensional Semiconductor Amplifiers Operating at 1.55 $mu{hbox{m}}$

We report time-resolved measurements of the linewidth enhancement factors (-factors) , and , associated with the adiabatic carrier recovery, carrier heating, and two-photon absorption dynamical processes, respectively, in semiconductor optical amplifiers (SOAs) with different degrees of dimensionality-one InAs/InGaAsP/InP quantum dot (0-D), one InAs/InAlGaAs/InP quantum dash (1-D), and a matching InGaAsP/InGaAsP/InP quantum well (2-D)-all operating near 1.55- wavelengths. We find the lowest values in the QD SOA, 2-10, compared to 8-16 in the QW, and values of and that are also lower than in the QW. In the QD SOA, the -factors exhibit little wavelength dependence over the gain bandwidth, promising for wide-bandwidth all-optical applications. We also find significant differences in the -factors of lasers with the same structure, due to the differences between gain changes that are induced optically or through the electrical bias. For the lasers we find the QW structure instead has the lower -factor, having implications for directly modulated laser applications.     

Photoluminescence and interface abruptness in InGaAsP/InGaAsP quantum wells

Quantum well (QW) structures consisting of InGaAsP wells and InGaAsP barriers grown by gas-source molecular beam epitaxy have been examined by low temperature photoluminescence (PL) in order to evaluate the contributions of compositional fluctuations in the quaternary alloy and of interface roughness to the PL linewidth. The well material was InGaAsP with a bandgap corresponding to a wavelength of 1.3 μm and the barrier material was InGaAsP of 1.15 μm. The theory for QW excitonic linewidths as a function of well thickness L_z due to fluctuations in alloy composition has been extended to include the case of the quaternary InGaAsP barrier. If the interfaces are atomically abrupt, the linewidth is dominated by compositional fluctuations in the well at large L_z and compositional fluctuations in the barrier at small L_z. The theory predicts a weak dependence of the linewidth on L_z since the composition of the well and barrier are similar. For rough heterointerfaces, the theory indicates the usual increase in linewidth with decreasing L_z. Photoluminescence measurements at 13K in arrays of single InGaAsP/InGaAsP QWs with L_z from 1.0 to 6.0 nm show only a weak variation of the full width at half maximum (FWHM) with L_z, in agreement with the theory for smooth interfaces. Furthermore, the lowest measured FWHM of 8.9 meV was found for a narrow well of L_z=1.8 nm, indicating the InGaAsP/InGaAsP interfaces are smooth and that the PL linewidth is dominated by compositional fluctuations.     

Estimation of drift mobility in InGaAsP semiconducting alloys from photoluminescence at 77 and 300 K

In this work, we propose a method of calculation for estimating the drift mobility from photoluminescence (PL). The method is based on the difference between the temperature of the scattered carriers after thermalization and the lattice temperature. The effective carrier temperature T_E was determined experimentally by fitting the high-energy region of PL spectra. The total mobility is obtained from the mobility calculated for different scattering mechanisms and the application of the Matthiessen rule. The method was used on InGaAsP semiconducting alloys grown by liquid phase epitaxy. The calculated mobility values for different InGaAsP samples agree with those reported for these alloys.     

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.     

The effect of barrier composition on the vertical carrier transport and lasing properties of 1.55-/spl mu/m multiple quantum-well structures

In this paper, the effect of barrier bandgap and composition on the optical performance of 1.55-/spl mu/m InGaAsP/InGaAsP and InGaAsP/InGaAlAs multiple quantum-well structures and Fabry-Perot lasers is evaluated experimentally. Direct vertical carrier transport measurements were performed through strain-compensated multiple quantum-well (MQW) test structures using femto-second laser pulse excitation and time-resolved photoluminescence up-conversion method. MQW test structures were grown with different barrier composition (InGaAsP and InGaAlAs) and barrier bandgap (varied from /spl lambda//sub g/= 1440 to 1260 nm) having different conduction band /spl Delta/E/sub c/ and valence band discontinuity /spl Delta/E/sub v/, while keeping the same InGaAsP well composition for all the structures. The ambipolar carrier transport was found to be faster in the structures with lower valence band discontinuity /spl Delta/E/sub v/. Regrown semi-insulating buried heterostructure Fabry-Perot (SIBH-FP) lasers were fabricated from similar QWs and their static light-current-voltage characteristics (including optical gain and chirp spectra below threshold) and thermal characteristics were measured. Lasers with InGaAlAs barrier showed improved high-temperature operation, higher optical gain, higher differential gain, and lower chirp, making them suitable candidates for high-bandwidth directly modulated uncooled laser applications.     

Characterization of radiative efficiency in double heterostructures of InGaAsP/InP by photoluminescence intensity analysis

The photoluminescence (PL) intensity of an InGaAsP layer has been investigated as a function of excitation power density over a wide range of five orders. Two samples with n-InP/n-InGaAsP isotype and p-InP/n-InGaAsP heterotype doping have quite different excitation power dependences on PL intensity. The heterotype sample has notable nonlinear dependence. The excitation power dependences of PL intensity are theoretically analyzed. The estimated interface recombination velocity of the InP/InGaAsP heterojunction is found to be very low (smaller than a few cm/sec), compared with that of a GaAs/GaAlAs heterojunction.This PL intensity analysis has been applied to study the effect of an InP buffer layer and thermal degradation of radiative efficiency. The effective non-radiative recombination life time has been estimated as about 2×10⁻⁹ s for the double heterostructure with no buffer layer. Annealing in conditions of low phosphorus pressure leads to degradation of radiative efficiency, and the degradation is attributed to decrease in the nonradiative life time in the quaternary layer rather than increase in the interface recombination velocity. Sufficient phosphorus pressure prevents degradation of radiative efficiency. The correlation between PL intensity and output optical power of the light emitting diode has also been investigated. The PL intensity must be measured at high excitation power if it is to accurately predict the output power as a light emitting diode.     

Low-current 1.3 ?m edge-emitting LED for single-mode-fibre subscriber loop applications

Index-guided InGaAsP edge-emitting LEDs couple 7 ?W into single-mode fibre at a drive current of only 20 mA. These devices can be modulated at data rates in excess of 432 Mbit/s, and their operating characteristics are ideal for single-mode-fibre subscriber loop applications.     

InGaAsP channel HFET's on InP for OEIC applications

A model for the calculation of the input noise of a high impedance photoreceiver is proposed, taking into account the contributions of low-frequency characteristics of the FET. Simulations based on this approach show that excess gate leakage current and low-frequency excess noise, usually observed in InGaAs channel FET's, strongly penalize the photoreceiver sensitivity for low to medium data rates. New InGaAsP channel HFET's have been developed and fabricated to solve those problems, dc measurements on 1×100 μm² gate HFET's show good I_ds-V_ds characteristics with associated gate leakage currents lower than 200 nA. Promising ft of 18 GHz and f _max of 40 GHz have been recorded on 0.5×200 μm² gate transistors. Low-frequency gate and channel noise measurements demonstrate the suitability of InGaAsP channel HFET structure and technology for low noise applications. A hybrid pin-HFET high impedance photoreceiver has been assembled with a 1×150 μm ² gate transistor. A very close agreement is found between photoreceiver input noise predicted by our model and experimental results. Record sensitivities of 34.8 dBm at 622 Mbit/s and -28.7 dBm at 2.5 Gbit/s are inferred from noise measurements, confirming the strong potential of InGaAsP channel HFET's for the fabrication of high sensitivity photoreceivers operating at moderate data rates     

Low-current 1.3-µm edge-emitting LED for single-mode fiber subscriber loop applications

Light-emitting diodes coupled to single-mode fiber can offer an economical and reliable alternative to the use of diode lasers in many single-mode fiber systems. This paper describes index-guided InGaAsP edge-emitting LED's (ELED's) which couple 7 μW into single-mode fiber at a drive current of only 20 mA. The devices exhibit rise times of less than 1.5 ns and can be modulated at data rates in excess of 432 Mbit/s. Operating characteristics of these low-current ELED's are well-suited for single-mode fiber subscriber loop applications.     

InGaAsP/InGaAs双结太阳电池研究

本文采用MOCVD设备生长了与InP晶格匹配的InGaAs(P)光伏器件。分析了InGaAsP/InGaAs (1.07/0.74 eV)双结太阳电池的QE与I-V特性。在AM1.5D光谱下,InGaAsP/InGaAs双结太阳电池的开路电压,短路电流,填充因子及转换效率分别为0.977 V, 10.2 mA/cm,80.8%,8.94%。对于InGaAsP/InGaAs双结太阳电池,在聚光条件下,其最大转换效率在280个聚光倍数下达到了13%。这一结果预示了GaInP/GaAs/InGaAsP/InGaAs四结太阳电池的潜在应用前景。     

A comparative study of phase modulation in InGaAsP/InP andGaAs/AlGaAs based p-i-n and p-p-n-n structures

A theoretical study of the phase modulation in InGaAsP/InP and GaAs/AlGaAs double heterostructure waveguides in the p-i-n and p-p-n-n configurations at wavelengths of 1.3 and 1.55 μm. is reported. The carrier-induced effects (plasma, band filling, and many body) and the field-induced effects (linear electrooptic and electro-refractive) are considered to calculate the change in the refractive index. Both structures made of InGaAsP/InP show higher modulation efficiency than the corresponding structures made of GaAs/AlGaAs in almost all the cases considered due to a larger index change in InGaAsP as its bandgap wavelength is closer to both 1.3 and 1.55 μm     

A comparative study of temperature sensitivity of InGaAsP andAlGaAs MQW lasers using numerical simulations

We used numerical simulation to compare the temperature sensitivity of an InGaAsP MQW laser emitting at 1.55 μm and an AlGaAs MQW laser at 0.82 μm. By artificially changing the InGaAsP laser gradually into a structure similar to the AlGaAs laser, we gained quantitative insight into how each material or structural parameter causes the relatively low T₀ of the InGaAsP MQW laser. Using a typical MQW structure we demonstrated the relative importance of parameters involving Auger recombination, current leakage over the quantum barrier, optical confinement and band offset. We found that if these parameters were made the same as the AlGaAs laser, the T₀ of the InGaAsP laser was even better than that of the AlGaAs laser. Our numerical simulation confirmed that the Auger recombination is the main cause of low T₀ in MQW InGaAsP lasers. We also discovered that thermal current leakage over the barrier and Auger recombinations are correlated with each other and both factors must be improved to increase the T₀ of InGaAsP lasers to that of AlGaAs lasers     

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.     

The growth of high quality InP/InGaAs/InGaAsP interfaces by CBE for SCH multi-quantum well lasers

Bulk InGaAsP and heterointerfaces of InP/InGaAs and InGaAsP/InGaAs have been grown by chemical beam epitaxy for use in multi-quantum well separate confinement heterostructure lasers. InGaAsP has been successfully grown for λ=1.1, 1.2 and 1.4 μm. The TMI and TEG incorporation coefficients have strong dependencies on substrate temperature and also charge as the InGaAsP composition tends towards InP. InP/InGaAs and InGaAsP/InGaAs quantum wells have been grown to determine the optimum gas switching sequence to minimize the measured photoluminescence FWHM. InGaAs quantum wells as narrow as 0.6 nm have been grown with 7K FWHM of 12.3 meV. Lattice matched MQW-SCH lasers were grown using different interface switching sequences with the best laser having a threshold current density of 792A/cm² for an 800 × 90 μm broad area device.     

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)