InGaAsP Research Articles

Long-wavelength ridge-wave-guide lasers with processed facets and integrated back-facet monitors

InP–InGaAs cleaved-cavity lasers are routinely used in long-wavelength optical transmission systems, packaged with a discrete pin photodiode back-facet monitor used to provide feedback to control the laser output power. This conventionally requires two separate wafer-fabrication processes, and individual testing, cleaving, and assembly at the chip level. The handling of cleaved bars, facet-coating, testing, and mounting is labour-intensive and expensive. Etching mirror facets during wafer processing makes it possible in a single fabrication process to fabricate lasers with an integrated back facet monitor, and do on-wafer testing without further alignment and assembly. This has now been achieved with the following technologiesf (i) laser epitaxial layers used for light detection as well as emission, (ii) reactive-ion-etched (RIE) (CH4–Ar)-etched mirror facets, and (iii) electrical interconnects by metal airbridges. Integrated laser and (or) monitors with RIE-processed facets have threshold currents as low as 30 mA, efficiencies of 0.14 mW mA−1, and monitor efficiencies of 0.1 mA mW−1. Excellent uniformity was observed across a 2 in (1 in = 2.54 cm) wafer. The lower threshold currents (27 mA) observed for cleaved facet lasers from the same wafer indicate that the processed facet quality can be further improved; the optimum RIE process results in etched facets with a facet angle about 5° off vertical. Packaged devices have been successfully operated at speeds up to 1 Gb s−1 for both laser and monitor. Preliminary reliability studies are described.

Fully self-aligned N- p- n InGaAs/InP HBTs with evaluation of their microwave characteristics

We present results on high-performance fully-self-aligned InGaAs InP SHBTs. A transit frequency ƒ T = 77 GHz and a maximum oscillation frequency ƒ max = 40 GHz at a collector-emitter voltage of V CE = 2 V and a collector current of I C = 40 mA have been achieved for transistors with an emitter area of 4 × 16 μm 2. Maximum noise figures of F min = 3.5 dB at 2 GHz and F min = 5.5 dB at 18 GHz are obtained at I C = 1 mA collector current.

High-speed InP/InGaAs avalanche photodiodes with a compositionally graded quaternary layer

InP/InGaAs avalanche photodiodes (APDs) with a compositionally graded quaternary layer at the heterointerface between the InGaAs absorption and InP multiplication regions were fabricated and tested. A comparison of samples with the graded layer and with conventional three quaternary layers showed that the frequency characteristics for samples with the graded layer did not deteriorate at a low bias voltage even below -100 degrees C, unlike APDs with three InGaAsP layers. Thus, no hole trapping occurred at the InP/InGaAs heterointerface with the graded layer. A sample with the graded layer showed a cutoff frequency exceeding 9 GHz at a low multiplication factor of 2. The authors found InP/InGaAs APDs with the compositionally graded quaternary layer to be useful over a wide temperature range.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

InGaAs/InP double-heterojunction bipolar transistors with step graded InGaAsP between InGaAs base and InP collector grown by metalorganic chemical vapor deposition

We have fabricated InGaAs/InP double-heterojunction bipolar transistors (DHBTs) grown by metalorganic chemical vapor deposition (MOCVD). By inserting step graded InGaAsP layers between p+-InGaAs base and n−-InP collector, the current gain of DHBTs with the graded layers was about twice as large as that without the graded layers, and the dependence of collector current on collector/emitter voltage was smaller than that without graded layers. The current gain was measured up to 2300 with 25×25 μm2 emitter area at a collector current density of 1×104 A/cm2.

Optical investigation of the band offsets in an InGaAs-InGaAsP-InP double-step quantum well

We report optical investigations of an InGaAs-InGaAsP-InP double step quantum well designed to provide a sensitive measurement of the band offsets in this technologically important system. Our results yield a conduction band offset to band gap difference ratio of 43±2 %. This value coincides with recent determinations of this parameter in the InPInGaAs heterojunction.

Dynamics of emission from an (InGa)AsP heterolaser with two-channel lateral confinement

An investigation was made of the dynamics of amplitude modulation of 1.3-μm radiation emitted by highly efficient low-threshold stripe heterolasers with lateral confinement due to two parallel epitaxial buried channels in a double heterostructure. The rise time of the transient characteristic was 0.1–0.6 ns, depending on the modulation regime. Single radiation pulses of duration less than 70 ps and regular trains of such pulses of frequency ~ 1 GHz were generated. The amplitude-frequency characteristics were determined under weak modulation conditions.

Type II to type I conversion of pseudomorphic GaAs on InP dependent on growth direction

Predictions of band offsets assign a type-II offset for the GaAs–InP interface without inclusion of strain effects, with the conduction- and valence-band-edge offsets approximately given by 0.4 and 0.3 eV, respectively. It has been demonstrated recently that pseudomorphic GaAs grown on [100]-oriented InP also has a type-II interface, but with the conduction-band offset reduced by the hydrostatic deformation potential of GaAs. Poisson’s ratio in GaAs for [111]-directed uniaxial stress is smaller by 40% than the value for [100]-directed stress. The lattice constant perpendicular to the growth interface is therefore not reduced as much for [111] growth compared with the [100]-growth case, leading to a consequently larger shift of the conduction-band-edge energy. Based on the recently measured value of −9 eV for the conduction-band-edge hydrostatic deformation potential in GaAs, the band offset for pseudomorphic GaAs grown on (111) InP has been calculated to be type I. This material system should therefore show type II to type I conversion dependent on the growth direction of the pseudomorphic layer. The issues involved in the growth and measurement of GaAs grown on (111) InP are discussed briefly.

Intermixing of InGaAs/InP multiple quantum well structures by Ga implantation

The effect of Ga implantation and thermal annealing on InGaAs/InP multiple quantum well structures is investigated by photoluminescence (PL) and sputtering Auger electron spectroscopy. It is found that the interdiffusion of both column III and column V atoms occurs at the interfaces between InP barrier and InGaAs well layers, but the degree of intermixing near the sample surface is small. The variations of PL peak energy shift with annealing and dose suggest that the PL peak shift is attributed to a combination of intermixing and stress.

Free carrier effects on the optical properties of InGaAsInP quantum wells

In this paper we present photoluminescence (PL) and photoluminescence excitation (PLE) spectra as a function of electron sheet carrier density (n s) in a Schottky gated 110 Å wide InGaAsInP quantum well. Major free carrier effects are observed on both the PL and PLE spectra. The PL spectra show a high energy cut-off at the electron Fermi energy for n s = 1.4 × 10 11 cm −2. As n s tends to zero the PL linewidth decreases from the high energy side, as expected for free carrier broadening. At the same time the n=1 transitions observed in PLE show a marked increase in oscillator strength and narrowing as n s tends to zero. The PLE results are discussed in terms of phase space filling and the variation of many body effects as a function of n s. The many body nature of the PLE transitions at the Fermi energy, for finite n s, is further demonstrated by the anomalous temperature dependence of the n=1 heavy hole transition.

Photoluminescence and magneto-transport of wide InGaAsInP modulation doped quantum wells

A photoluminescence (PL) study of 700Å wide modulation doped InGaAsInP quantum wells in magnetic fields up to 10 Tesla, is reported. PL from the lowest electron sub-bands, localised in the space charge potentials at the two sides of the QW, and from higher delocalised sub-bands extending across the whole width of the QW, is observed. The performance of simultaneous Quantum Hall Effect (QHE), Shubnikov-de-Haas and PL measurements is found to be crucial to obtain a reliable understanding of the behaviour of the PL spectra in magnetic field. In particular the QHE provides direct information on the number of filled sub-bands and Landau levels in a complicated system of total carrier density ∼10 12 cm −2, containing several populated electronic sub-bands.

Photoluminescence study of the density-of-states between Landau levels in the quantum hall effect system

Very well resolved electron Landau levels (LLs) are observed in the photoluminescence spectra of modulation-doped InGaAsInP quantum wells. An upper limit for the density-of-states (DOS) between LLs of 0.036 D 0 is reported, at a filling factor of ν = 4, where D 0 is the two dimensional DOS at zero magnetic field. This spectroscopic value contrasts strongly with that deduced from measurements sensitive only to the form of the DOS at the Fermi energy. Anomalies in the Landau level transition energies as a function of field are discussed.

Resonant tunneling in InGaAsInP double-barrier structures and superlattices

We have studied the perpendicular transport in the double-barrier structures of the InGaAs system, with particular focus on reducing the large leakage current caused by conduction at the perimeter of the device. Results obtained on a sample which had low doping in the electrode layers, such that the Fermi level of the emitter electrode was below the first subband level at low bias, are presented. These results demonstrate unambiguously that the process of selectively etching the device has been successful in suppressing the leakage current. A peak-to-valley ratio of 4.3 was obtained for this sample at 4.2K. We have also carried out the first investigation of the perpendicular transport in InGaAs superlattice structures. These structures exhibit a large series of periodic negative differential resistance whose number and period are controlled by the number of the width of the quantum wells respectively.

Analog frequency modulation of radiation emitted by single-mode heterojunction lasers in the spectral range 1.3μ

The emission spectra of two single-mode heterojunction lasers based on InP–(InGa)AsP structures were determined with a resolution of 50 MHz under conditions of modulation by a small signal superimposed on a constant injection current. The dependences of the frequency modulation coefficient on the frequency of the modulating signal were determined in the range 102–3×109 Hz. These dependences were influenced considerably by the structure and the mounting of the active element.

Optical amplification in an (InGa)AsP heterostructure in the spectral range 1.3 μ

The spectral dependence of the optical gain was determined for an injecting double heterostructure with a strip active waveguide made of (InGa)AsP. The gain maximum at room temperature corresponded to the wavelength of 1.28 ..mu... Gain saturation by superradiance in a waveguide of 1.2 mm length was observed when the injection current density was 1.3 x 10/sup 4/ A/cm/sup 2/. The single-trip gain reached 27 dB.

Characterization of Defects in Liquid Phase Epitaxial InP and InGaAsP Crystals by Scanning Electron Microscopy and Electron Beam Induced Current Method

Observation de defauts de surface, trous, crateres, defauts mecaniques et de defauts de volume, dislocation interfaciale, striations, dislocations inclinees et inclusions

Optical investigation of MQW system InP–InGaAs–InP

A new multiquantum well system, InP–InGaAs–InP, has been grown by the chloride transport vapor phase epitaxy. The Auger measurements show that a very sharp InGaAs–InP heterointerface (less than 30 Å) can be obtained by the present growth system. Optical absorption and photoluminescence measurements give the evidence for the formation of the quantum wells in InGaAs layers. Temperature dependence of photoluminescence indicates that the dominant emission at low temperatures is interpreted as the band-to-acceptor transition. It also shows that temperature dependence of the transition energy from hole subband to electron subband is apparently affected by the thickness of the quantum well. Two models are presented for this. One takes into account the localized phonons in the InGaAs–InP heterointerface region whose frequency is higher than that in the bulk samples. The other considers the difference in the thermal expansion coefficients of InGaAs and InP, which reduces a shift of the [000] conduction band minimum of the InGaAs quantum well layer toward higher energy with decreasing temperature.

Electronic properties of MO–CVD grown InGaAs–InP heterojunctions and superlattices

We present optical and magnetotransport experiments performed in InGaAs–InP heterojunctions and superlattices grown by metalorganic chemical vapor deposition. These investigations give evidence of the two-dimensional nature of these new structures, and also some information on their electronic properties.

Lattice defects in LPE InPInGaAsPInGaAs structure epitaxial layers on InP substrates

Lattice defects generated during LPE growth of InPInGaAsPInGaAs structure epitaxial layers on InP substrates are studied. Two different kinds of dislocations are observed at the two interfaces of the epitaxial layers; at the InPInGaAsP interface, misfit dislocations are generated in the InP layer by carry over of InGaAsP melt into the InP one and at the InGaAsInP interface, Vshaped dislocations are generated in the InGaAs layer. It is shown that the critical amount of lattice mismatch to suppress generation of misfit dislocations in InP is about two times smaller than that of other III–V compound semiconductors. Conditions to suppress the generation of these dislocations are clarified. Gitterdefekte, die wahrend des LPE-Wachstums von epitaktischen InP-InGaAsPInGaAsStrukturschichten auf InP-Substraten erzeugt werden, werden untersucht. Zwei verschiedene Arten von Versetzungen werden an den beiden Grenzflachen der Epitaxieschichten beobachtet; an der InPInGaAsPGrenzflache werden Misfit-Versetzungen in der InP-Schicht durch Ubergang der InGaAsP- in die InP-Schmelze erzeugt, an der InGaAs-IP Grenzflache werden V-formige Versetzungen in der InGaAs-Schicht generiert. Es wird gezeigt, das der kritische Wert der Gitterfehlanpassung zur Unterdruckung der Generation von Misfitversetzungen in InP zweimal kleiner ist als der in anderen III–V-Verbindungshalbleitern. Die Bedingungen zur Unterdruckung der Versetzungsbildung werden erlautert.

InGaAs avalanche photodiode with InP p - n junction

A new InGaAs avalanche photodiode structure that has an InGaAs light absorption region and InP avalanche multiplying region is proposed. A dark-current density of 2.2 × 10-3 A/cm2 at 90% of breakdown voltage and a multiplication factor of 45 were obtained for the new structure diode fabricated from a liquid-phase epitaxially grown wafer.

An uhv system for in situ preparation and analysis of thin films and surfaces : Y. Shapira and E. Grunbaum. Vacuum28, (12) 523

To meet the requirement of photon-starved detection, separate absorption grading charge multiplication avalanche photodiodes (SAGCM APDs) have drawn more and more attentions. In this work, we presents a detailed analysis of dark currents for planar-type SAGCM InGaAs–InP APDs with different sub-micron thicknesses of multiplication layer, considering the effect of the diffusion process, generation-recombination process and tunneling process. According to our knowledge, it is the first time clearly demonstrating that the dominant component of dark current for a SAGCM APD changes with multiplication gain from surface to volume contribution. Our finding could be beneficial to the optimization of an APD with a SAGCM structure. An optimal InGaAs–InP APD with low-voltage operation (<40 V) in combination with ultra-low dark current (0.10 [email protected]M = 8) has been demonstrated.