Fe-doped Semi-insulating InP Research Articles

Photocurrent contrast in semi-insulating Fe-doped InP

The relation between photocurrent and iron distribution in as-grown bulk InP is studied on the basis of a theoretical model that considers the electronic transitions involving and electronic levels. The photocurrent contrast is thus analysed in terms of fluctuations in and . When studying the homogeneity of Fe-doped semi-insulating InP wafers by means of scanning extrinsic photocurrent microscopy, it is seen that inhomogeneity is mainly controlled by fluctuations of the neutral iron concentration .

Positron transport studies at the Au - (InP:Fe) interface

Positron mobility and lifetime measurements have been carried out on semi-insulating Fe-doped InP samples with Au contacts used for electric field application. The lifetime measurements, with electric fields directed towards the Au - InP:Fe interface, reveal no component associated with interfacial open-volume sites and thus give no evidence of any positron mobility. The mobility measurements, made using the Doppler-shifted annihilation radiation technique, however, reveal a temperature independent positron mobility of about in the range 150 - 300 K. These observations, together with results from I - V analysis, are discussed with reference to two possible band-bending schemes. The first, which requires an ionized shallow donor region adjacent to the Au - InP interface, seems less plausible on a number of grounds. In the second, however, an negative space charge produces an adverse diffusion barrier for positrons approaching the interface together with a non-uniform electric field in the samples capable of explaining the observed mobility results.

DC characterization of fully ion-implanted p-n junctions into semi-insulating InP

The forward and reverse characteristics of p/sup +/-n junctions made by Mg and Si implantation and rapid thermal annealing into Fe-doped semi-insulating InP are described. The effects of the Si dose for obtaining the n-type region, the use of P co-implantation for obtaining the p/sup +/ region, and the annealing time are studied. The dominant conduction mechanism at forward bias was found to be recombination in the space-charge region, with ideality factors of n=2 down to 198 K, and temperature dependence with an activation energy of 0.76 eV. The reverse characteristics presented junction breakdown at voltages around -20 V, and were accurately described by a thermally-activated trap-assisted tunneling mechanism. The energy of the corresponding trap, obtained by the fitting of the experimental characteristics, was 0.6 eV, and its origin was tentatively ascribed to the Fe deep acceptor present in semi-insulating InP.

Observation of In antisite and Fe-related defects in 30-MeV electron-irradiated Fe-doped semi-insulating InP.

Photoluminescence (PL) spectra are reported and assigned to the ${\mathrm{In}}_{\mathrm{P}}$ antisite in undoped and Fe-doped semi-insulating InP which was irradiated by 30-MeV electrons. In Fe-doped samples, the two PL emissions are at 30 and 117 meV above the valence band, and annihilate in an annealing stage from 300 to 350 \ifmmode^\circ\else\textdegree\fi{}C. ${\mathrm{In}}_{\mathrm{P}}$ defects in undoped samples are \ensuremath{\sim}${10}^{2}$ times smaller than those produced in Fe-doped InP. In Fe-doped samples, an emission is also observed near an emission relating to the deep ${\mathrm{In}}_{\mathrm{P}}$ level. The produced defect is suggested to be a complex defect consisting of an iron impurity and an electron-irradiation-induced phosphorous vacancy.

Electron-Irradiaton Induced Defects in Fe-Doped Semi-Insulating InP

Electron-Irradiaton Induced Defects in Fe-Doped Semi-Insulating InP

Study of deep level defect behaviour in rapid thermal annealed Fe-doped semi-insulating InP

The effects of rapid thermal annealing (RTA) on deep level defects behaviour in Fe-doped semi-insulating InP has been studied by photoinduced current transient spectroscopy. Three samples were annealed at 600 °C, 700 °C and 800 °C for a fixed plateau duration of 15 s in a RTA commercially-available furnace. We show that RTA leads to the disappearance of the usually observed 0.66 eV Fe-related level and the formation of three deep traps having the activation energies 0.1, 0.31 and 0.54 eV. The possible involvement of phosphorus vacancy related complexes and the metastability of iron in the compensation mechanism after annealing is suggested.

Evidence of point defect supersaturation during Zn diffusion in InP single crystals

Formation of defects during Zn diffusion into undoped and semi-insulating Fe-doped InP single crystals at 700 °C was observed by transmission electron microscopy for various diffusion conditions. Agglomerates of predominantly perfect interstitial-type dislocation loops, dislocations, and small indium precipitates inside voids are observed in the Zn-diffused crystal region. In addition, large planar arrays of precipitates are formed by climbing dislocations. From these observations it is concluded that the incorporation of Zn on In sublattice sites creates a supersaturation of In self-interstitials which is relieved by dislocation loop formation leading to a supersaturation of P vacancies and void formation.

Photocurrent study of Fe-doped semi-insulating InP

Fe distribution is studied in semi-insulating liquid-encapsulated Czochralski (LEC) Fe-doped InP, by means of spatially resolved photocurrent measurements. Local fluctuations of the extrinsic photocurrent are related to Fe distribution inhomogeneities, which are related to the dislocation atmospheres. The electronic transitions involved are modelled by a set of rate equations. The theoretical model gives an excellent fit of the experimental data, thus allowing us to obtain an estimation of the local Fe 3+ concentration, which can fluctuate by up to 15% of the average concentration.

Characterization of the homogeneity of semi-insulating InP by the spatially resolved photocurrent

Semi-insulating Fe-doped InP wafers have been studied by a spatially resolved photocurrent technique. The photocurrent fluctuations are interpreted on the basis of either N D −N A or [ Fe +3] variations, resulting in non-homogeneous electric local compensation, owing to local variations in either the total electrically active Fe concentration or the net donor concentration. Growth striations are revealed, showing differences in the local photocurrent fluctuation at different parts of the wafers, these being barely observable in the wafer edge.

An InP-based optothyristor for pulsed power-switching applications

A high-power InP-based optothyristor has been fabricated and tested for pulsed power switching. To increase the power handling capability, the device has a 250 mu m-thick Fe-doped semi-insulating (SI) InP sandwiched between two p-n junctions grown by MOCVD. The device turn-on is controlled by optical illumination on the SI-InP, which creates a high concentration of electron and hole pairs. The switched current and the di/dt rating have been studied as a function of the switch blocking voltage. It is shown that the optothyristor is capable of switching a current almost four times the current switched by a bulk SI-InP photoconductive switch under the same voltage bias.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

InP-based MIS-type FETs

An analytical model for a depletion mode MIS-type FET having a charge-depleted semiconducting layer as a barrier layer has been developed. It has been applied to two InP-based structures in which a semi-insulating Fe-doped InP layer is used as the insulating gate of the FET and the calculated current-voltage characteristics for them are presented.

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.

Characterization of deep level defects in thermally annealed Fe-doped semi-insulating InP by photoinduced current transient spectroscopy

Photoinduced current transient spectroscopy has been used to show the effect of thermal annealing on deep level defects in semi-insulating Fe doped InP wafers. The annealing experiments have been accomplished in an infrared image furnace during 15 min at temperatures ranging from 663 to 820 °C. We show that this treatment leads to the formation of four deep traps named T1–T4 having the following activation energies: 0.14, 0.21, 0.41, and 0.53 eV, respectively. We show that the thermal anneal at high temperature leads to deterioration of the electrical properties of the material.

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.

Traps in semi-insulating InP studied by thermally stimulated current spectroscopy

Traps in Fe-doped semi-insulating InP samples have been studied by thermally stimulated current spectroscopy with IR (hν≤1.12 eV) excitation at 81 K. The possible involvement of native defects in determining the compensation mechanisms is suggested based on the observation of other than the usual 0.64 eV Fe-related activation energy for the dark current in one of the four samples supplied from different sources. A metastable behavior of traps in another sample was found and explained by a charge-controlled defect reaction model. Three out of the six traps observed are suggested to be electron traps and one among the other three traps is believed to be a hole trap.

High-speed 1.3-μm InGaAsP buried crescent lasers with Fe-doped InP current blocking layers grown by organometallic vapor phase epitaxy using tertiarybutylphosphine

Fe-doped semi-insulating InP layers grown by low-pressure organometallic vapor phase epitaxy with tertiarybutylphosphine have been used as a current block layer for high-speed 1.3-μm InGaAsP buried crescent lasers. The performance characteristics of such lasers are comparable to those of lasers with a PH3-grown Fe-doped semi-insulating InP current blocking layer over a measurement temperature range of 25 to 85 °C. A 3-dB modulation bandwidth of 17.5 GHz has been obtained at room temperature and a cw bias current of 100 mA.

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.

A monolithic 5 Gb/s p-i-n/HBT integrated photoreceiver circuit realized from chemical beam epitaxial material

The authors report on a high performance monolithic photoreceiver fabricated from chemical beam epitaxy (CBE) grown InP/InGaAs heterostructures, incorporating a p-i-n photodetector followed by a transimpedance preamplifier circuit configured from heterojunction bipolar transistors (HBTs). The optoelectronic integrated circuit (OEIC) was fabricated on a semi-insulating Fe-doped InP substrate. Microwave on-wafer measurements of the frequency response of the transistors yielded unity current gain cutoff frequencies of 32 GHz and maximum oscillation frequencies of 28 GHz for collector currents between 2 and 5 mA. The photoreceiver was operated up to 5 Gb/s, at which bit rate a sensitivity of -18.8 dBm was measured at a wavelength of 1.5 mu m. The results demonstrate that the CBE growth technique is suitable for high performance HBT-based OEICs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A.c. properties of semi-insulating InP

Abstract The electrical conductivity of Fe-doped semi-insulating (SI) InP was measured between 77 K and 360 K over the frequency range 10 Hz-100 kHz. The conductivity at room temperature is of order 10−8 S cm−1, the activation energy being 0·64 eV. Below ∼250 K the conductivity is frequency dependent, varying with frequency as [sgrave](f)∼f s, where s∼1, and is only weakly thermally activated (∼0·01 eV). In the same frequency and temperature ranges we have also measured the permittivity of this material. Its value at 77K is ∼11.9 and its temperature coefficient amounts to 2·5×10−4K−1. In addition the permittivity has been investigated under high hydrostatic pressure up to 1 GPa. The pressure coefficient of permittivity has been found to be -2×10−2 GPa−1. The results obtained are discussed within the framework of a simple model.