Semi-insulating InP Substrate Research Articles

Photoluminescence properties of the Al0.48In0.52As/InP interface and the diffusion of carriers thereto

A study of the photoluminescence (PL) and photoluminescence excitation (PLE) properties of the interface luminescence of the staggered-aligned Al0.48In0.52As/InP is presented, together with a study of the diffusion of carriers to this interface. Two PL peaks originating from the interface were measured at energies higher than commonly reported. This is the result of growth of the Al0.48In0.52As layer directly on the semi-insulating InP substrate, which results in a much sharper triangular well in the conduction band than when grown on an n-type InP buffer layer. Data from PL in a magnetic field and from PLE both showed that the PL transitions are excitonic in character. Furthermore, an inverted S-shape temperature dependence was found for the PL energy, which is characteristic of carrier localization. PLE measurements showed that at 4.2 K both electrons and holes participating in the interface PL are provided by exciton diffusion from the InP, while at 70 K they are provided by exciton diffusion from the Al0.48In0.52As. The difference arises from carrier localization in the Al0.48In0.52As top layer below 50 K. Unexpectedly, for the InP at 4.2 K the PL intensities of both excitonic and donor-to-acceptor transitions were independent of the absorption of laser light in the Al0.48In0.52As top layer.

High speed performance of 1.5 μm compressive-strained multiquantum-well gain-coupled distributed-feedback lasers

1.5 μm compressive-strained multiquantum-well gain-coupled distributed-feedback lasers have been fabricated on semi-insulating InP substrates with very low parasitic capacitance for studying the laser dynamic characteristics. A maximum 3 dB bandwidth of 12.8 GHz under small signal modulation, a 20 dB down chirping width of 0.33 nm under 5 Gbit/s NRZ pseudorandom modulation, and a low chirping short pulse of 20 ps under gain switching are obtained.

Role of a nucleation layer in suppressing interfacial pitting in

In this work, we investigate the role of a low temperature nucleation layer on the interfacial properties of InAs epilayers grown on (100) semi-insulating InP substrates using a two-step metalorganic chemical vapor deposition method. Cross-sectional and plan-view transmission electron microscopy studies were carried out on InAs films of nearly equal total film thicknesses but for different thicknesses of a nucleation layer of InAs deposited at low temperature on the substrate. Our studies show that thermal etchpits are created at the interface between the InAs film, and the InP substrate for thin nucleation layer thicknesses. This is because the low temperature nucleation layer of InAs does not cover completely the surface of the InP substrate. Hence, when the temperature is raised to deposit the bulk of the InAs film, severe thermal pitting is observed at the interface. These thermal etchpits are sources of threading dislocations. To obtain high quality InAs films and suppress interfacial pitting there is an optimum thickness of the nucleation layer. Also, our studies show that there is a relationship between the density of defects in the film and the thickness of the nucleation layer. This in turn relates to the variation of the electronic properties of the InAs films. We have observed that for all nucleation layer thicknesses, the density of threading dislocations is higher close to the interface than at the free surface of the film.

Laser-assisted thermally enhanced InP via etching for microwave device applications

A laser-based technique for thermally enhanced rapid etching of via holes through Fe-doped semi-insulating InP substrates is described. The process produces steep-walled closely-spaced via holes in etch times as short as 3-5 s/via in 100- mu m-thick substrates. This technique is key to the fabrication of low-inductance metallized via contacts critical for high-speed microwave and millimeter-wave devices and circuits. The laser-based technique is material selective, allowing both through-wafer and blind-hole etching which is terminated on metal circuit contacts. Via structures have been fabricated on semi-insulating InP substrates patterned with millimeter-wave device geometries. >

Fabrication/Characterization of a Pseudomorphic Ga0.1In0.9P/InP MESFET

ABSTRACTA pseudomorphic Ga0.1In0.9P/InP MESFET grown by low pressure metalorganic chemical vapor deposition(LP-MOCVD) has been fabricated and characterized. The results indicated a transconductance of 66.7 ms/mm and a saturation drain current (Idss) of 55.6 mA have been achieved; furthermore, the Schottky barrier on InGaP as high as 0.67eV can be obtained using Pt2Si as the gate material. For comparison, a conventional InP MESFET with 5μm gate length has also been fabricated on InP epitaxial layer grown by low pressure metalorganic chemical vapor deposition on Fe-doped semi-insulating InP substrate. The transconductance and Idss were found to be 46.7 mS/mm and 43.1 mA at zero gate, respectively, for the depletion mode n-channel MESFET with Au as the gate metal; whereas, for the MESFET using Pt2Si as the gate metal, a transconductance of 40.3 mS/mm and a saturation drain current of 41.1 mA at zero gate bias have been obtained. The results indicated that Ga0.1In0.9P/lnP MESFET has better performance than InP MESFET because of higher energy gap of Ga0.1In0.9P.

Zn-doped InGaAsP (1.3 μm) contact layer for an inverted DH laser structure

Zn as an acceptor in InGaAsP (1.3 μm) epilayers grown and doped by liquid-phase epitaxy was investigated for its dependence on growth parameters to establish optimum conditions for a bottom contact layer of a double-heterostructure (DH) laser diode monolithically integrated with its driver circuit on a semi-insulating InP substrate. Carrier concentrations, measured by the Van der Pauw technique and electrochemical C / V profiling (ECV), increase with the mole fraction of Zn added to the In melt until a maximum of about 1×10 19 cm -3 si reached. Nearly constant room temperature mobilities, which are larger than published data for Cd-doped InGaAsP, were obtained in a carrier concentration range of 1×10 18 to 1×10 19 cm -3. A minimum value of 1.3×10 -2 ω cm was achieved for the resistivity at room temperature. ECV profiling shows that, beyond the hole-concentration maximum, a further increase in the amount of Zn added to the growth solution leads to an enhanced outdiffusion of Zn into the InP substrate. Two diffusion fronts were observed, indicating that two different diffusion mechanisms take place. The crystal quality of the epitaxial layers was studied by photoluminescence microscopy and spatially resolved cathodoluminescence. Uniform luminescence images were obtained for the layers doped to the maximum hole concentration. Double crystal X-ray topography revealed extended regions where the lattice mismatch relative to the InP substrate is only of the order of 10 -7.

Monolithic integration of optoelectronic devices with reactive matching networks for microwave applications

Microwave impedance matching networks have been, for the first time, monolithically integrated with GaInAs p-i-n photodiodes and GaInAsP buried ridge stripe structure lasers ( lambda =1.3 mu m), both on a semi-insulating InP substrate. The microwave power transfer optical links were compared using matched and unmatched devices. Compared to an unmatched link, an improvement of 11.4 dB at 5.6 GHz (600 MHz bandwidth) is obtained for the totally matched one; this result corresponds quite well to the theoretical prediction (12 dB at 6 GHz).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transverse electric and transverse magnetic polarization active intersubband transitions in narrow InGaAs quantum wells

Polarization-resolved infrared spectroscopy has been used to demonstrate the existence of transverse electric (TE) and transverse magnetic (TM) active intersubband transitions in lattice-matched, unstrained In0.53Ga0.47As/In0.52Al0.48As and strained In0.7Ga0.3As/AlAs quantum wells grown by molecular beam epitaxy on Fe-doped semi-insulating InP (001) substrates. It is shown that a previously reported intersubband absorption peak at 0.3 eV in a 4.0-nm wide, lattice-matched InGaAs/InAlAs quantum well can be resolved into two peaks active for TE and TM polarizations, respectively, with a 10 meV splitting between them. Bound to quasibound state transition at 0.59 eV (2.1 μm) for a narrow, 2.8-nm-wide InGaAs quantum well has also been observed. Group symmetry analyses considering D2d symmetry, tetragonal perturbation of local crystal and strain deformation potential, and interface roughness of the ternary quantum-well structure is proposed to explain the polarization selection rules, and the Stark splitting in the intersubband absorption.

Single-step implant isolation of p+-InP with 5-MeV O ions

The applicability of a single, 5-MeV O implant for electrical isolation of epitaxial p+-InP layers on semi-insulating InP substrates has been investigated. For such an implant, the ion range is several times that of the epitaxial layer and, consequently, end-of-range disorder is buried deep within the substrate. Though sheet resistances of ∼5×106 Ω/sq were achieved, irradiation-induced conduction in the substrate limits the maximum sheet resistance attainable. The single, high-energy implant scheme has been compared with a multiple, low-energy implant sequence. For a given level of disorder in the epitaxial layer, the latter yields higher sheet-resistance values though the former offers significant process simplification.

An InGaAs/InP p-i-n-JFET OEIC with a wing-shaped p/sup +/-InP layer

A receiver optoelectronic integrated circuit (OEIC) structure with an InGaAs p-i-n photodiode, InGaAs self-aligned junction FETs and a bias resistor has been fabricated on a semi-insulating InP substrate. The fabrication processes are highly compatible between the photodiode and the JFET, and reduction in FET gate length is achieved using anisotropic selective etching and a two-step organometallic vapor phase epitaxy (OMVPE) growth schedule. The 80- mu m diameter p-i-n detector exhibits a leakage current of 2 nA and a capacitance of about 0.35 pF at -5 V bias voltage. Extrinsic transconductance and a gate-source capacitance of the JFET are typically 45 mS/mm and 4.0 pF/mm at 0 V, respectively. The maximum voltage gain of the preamplifier is 12.5 and the bandwidth of the p-i-n amplifier OEIC is expected to be about 1.2 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Liquid phase epitaxy growth of high purity InP using rare earth dysprosium gettering

Epitaxial layers of InP were grown on semi-insulating InP substrates by liquid phase epitaxy. The introduction of small amounts (4 × 10 −4 −1 × 10 −3 atomic fraction) of the rare earth dysprosium in the melt resulted in a substantial increase in electron mobility and a reduction in the electron concentration. The mobility increased from 2040 cm 2 V −1 s −1 (without dysprosium) to 4200 cm 2 V −1 s −1 (with dysprosium) at 300 K and from 2480 cm 2 V −1 s −1 to 19 250 cm 2 V −1 s −1 at 83 K. The carrier concentration accordingly decreased from 2.3 × 10 17 to 4 × 10 15 cm −3 (300 K). The results of secondary-ion mass spectrometry and photoluminescence measurements indicate that reduction in the dominant impurity silicon by gettering is responsible for the improved properties.

Initial Stages of Growth of Epitaxial InAs Films on InP Substrate

ABSTRACTIn this work we investigate the initial stages of growth of heteroepitaxial films of InAs on semi-insulating InP substrates using MOCVD. Very thin films grown at different temperatures, Tn, were studied using TEM and SEM. The 3.2% lattice mismatch between InAs and InP causes strains that are partially accomodated by the generation of misfit dislocations at the interface. Our studies indicate that the deposited InAs nucleates in the form of islands which then grow and coalesce to form the film. Elemental mapping studies indicate that the area of substrate covered by the film is a function of the growth temperature. The thickness of the film and the electron mobilities also vary with T°. The films with best mobilities were obtained for Tn = 480°C.

InGaAs/InP waveguide photodetector with high saturation intensity

An InGaAs/InP rib-loaded waveguide pin, photodetector integrated with a microwave coplanar waveguide transmission line on a semi-insulating InP substrate is demonstrated. The detector has a 3 dB frequency response in excess of 20 GHz. The DC responsivity of the waveguide photo-detector remains constant at 0.21 A/W over a range of incident optical powers from 400 μW to 20 mW.

High speed waveguide-integrated photodiodes grown by metal organic molecular beam epitaxy

Using InP/InGaAs layers grown by metal organic molecular beam epitaxy (MOMBE) on semi-insulating (SI) InP substrate we have fabricated waveguide-integrated pin-photodiodes working on the principle of evanescent field coupling. A 3dB cutoff frequency of 9.6 GHz has been found in a 50 Ω system. The 100 μm long diodes exhibit a capacitance of < 0.1 pF at −5 V bias. In addition design criteria are given to improve the speed of the devices.

Photoreflectance Characterization of the Semi-Insulating InP Substrate Interface with InGaAs and InAlAs Epilayers

ABSTRACTPhotoreflectance (PR) has been performed on a series of undoped and n-type, InGaAs and InAlAs molecular beam epitaxy (MBE) grown layers with different In mole fractions, and epilayer thicknesses on Fe-doped semi-insulating (SI)-InP substrates. From investigations of the temperature dependence, time constant dependence and an additional cw light beam intensity dependence, three substrate peaks are identified as an excitonic transition from the substrate, a free electron transition near the interface which gives a Franz-Keldysh oscillation (KFO), and a transition from the spin-orbit split-off valence band. The results are indicative of a redistribution of charge near the substrate interface in the process of MBE growth; the associated PR signal (phase) could be used for in-situ monitoring of epilayer growth on SI-InP wafers.

The phototransistor revisited: all-bipolar monolithic photoreceiver at 2 Gb/s with high sensitivity

The authors revisit the three-terminal phototransistor and demonstrate the application of the HPT (heterojunction phototransistor) at 2 Gb/s in an all-bipolar monolithic photoreceiver. They also show a performance comparable to the best p-i-n photoreceiver. The phototransistors were fabricated from epitaxial layers grown by metal-organic molecular beam epitaxy on a Fe-doped semi-insulating InP substrate. The phototransistor had a small-signal electrical current gain between 150 and 200. The quantum efficiency of the base-collector photodiode was 40%. Microwave on-wafer measurements yielded a unity current gain cutoff frequency of 30 GHz and a maximum oscillation frequency of 20 GHz at a collector current of 5.0 mA. The small-signal frequency response of the packaged monolithic photoreceiver indicated a 3-dB bandwidth of 1.1 GHz, at a wavelength of 1.53 mu m, with no peaking in the response.

OEICs for WDM transceiver modules fabricated by reactive ion etching on semi-insulating substrates

The design and fabrication of OEICs on semi-insulating InP substrates comprising 1300 nm DFB lasers, 1300/1530 nm wavelength duplexers and monitor photodiodes is described. OEIC lasing thresholds were as low as 20 mA. The through-state crosstalk for the integrated duplexer was typically -12 dB. Linear tracking of the laser output by the monitor photodiode was achieved with sensitivities in the region of 70 mu A/mW. The OEICs operated successfully in a 622 Mbit/s bidirectional optical link.

36-GHz static digital frequency dividers in AlInAs-GaInAs HBT technology

Static divide-by-four circuits have been fabricated that operate up to 36 GHz using AlInAs-GaInAs heterojunction bipolar transistor (HBT) IC technology processing an f/sub t/ and f/sub max/ of 110 and 73 GHz, respectively. The transistors used consisted of an abrupt emitter-base junction design which incorporated a low-temperature p-GaInAs spacer as part of the base to inhibit beryllium diffusion. The AlInAs-GaInAs HBT device layers were grown lattice-matched to semi-insulating InP substrates by solid-source molecular beam epitaxy (MBE).

Schottky barrier heights of n-type and p-type Al/sub 0.48/In/sub 0.52/As

The authors report electrical measurements on four different metal contacts which formed Schottky barriers to lightly doped complementary n- and p-type Al/sub 0.48/In/sub 0.52/As epitaxial material grown by molecular beam epitaxy on semi-insulating InP substrates. The Schottky contact metals studied were Au, Al, Pt, and tri-layer Ti/Pt/Au. The Schottky barrier heights varied from 0.560 eV for Al on n-type AlInAs to 0.905 eV for Al on p-type AlInAs, with intermediate values for the other metals studied. The sum of n- and p-type Schottky barrier heights for each metal contact ranged from 1.440 to 1.465 eV, in good agreement with the accepted Al/sub 0.48/In/sub 0.52/As bandgap value of 1.45 eV.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Manganese-related luminescence in GaInAs/AlInAs multiple quantum wells grown on InP by molecular beam epitaxy

Two Mn-related luminescence peaks have been observed in a series of nominally undoped Ga0.47In0.53As/Al0.48In0.52As multiple quantum wells (MQW) grown lattice-matched on InP substrates by molecular beam epitaxy. These two peaks correspond to on-center and on-edge impurity states, respectively. The origin of the Mn impurities is outdiffusion from the Fe-doped semiinsulating InP substrate into the epitaxial layer. The binding energy of Mn acceptors, determined to be 53±3 meV in bulk-like Ga0.47In0.53As, increases to 80±5 meV for the on-center Mn state in a 58 A MQW. The strong well-width dependence of the binding energy is explained in terms of the unique behavior of the Mn impurity in III–V semiconductors. The Mn in Ga0.47In0.53As and Ga0.47In0.53As/Al0.48In0.52As MQWs behaves predominantly as a deep impurity.