Showing papers by "Stephen J. Pearton published in 1988"

Donor-hydrogen complexes in passivated silicon.

Abstract: Several new infrared absorption bands have been discovered in hydrogen passivated silicon doped with P, As, and Sb. The frequency shift upon substitution of D for H confirms the assignment of these bands to donor-H complexes. Thermal annealing experiments, in which both the absorption due to complexes and to free carriers were measured, confirm that donor passivation is due to complex formation, and yield the stability of the complexes. Our results suggest that H is bonded to Si rather than the donor directly.

Defects in electronic materials

Abstract: This book collects papers on semiconductor materials. Topics include: oxygen precipitation formation, silicon, boron complexes in silicon, radiation-induced defects in indium antinomide, gallium arsenides, vapor phase epitaxy, gallium and indium phosphides, crystal doping, and deep level transient spectroscopies.

Vibrational spectroscopy of acceptor-hydrogen complexes in silicon: Evidence for low-frequency excitations.

Abstract: The infrared spectra of acceptor-H centers in passivated Si for B, Al, and Ga provide evidence for an unexpected low-frequency excitation of the complexes. The broad vibrational bands observed near 2000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at room temperature shift to higher frequency and narrow dramatically upon cooling to He temperature. While the B-H--related band remains structureless at intermediate temperatures, the vibrational bands observed for Al-H and Ga-H complexes show thermally populated sidebands to the low-energy side of the main vibrational bands. The sidebands indicate the presence of a low-frequency excitation of the complex. We have determined Boltzmann energies of 78 and 56 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ from the intensity of the sidebands as a function of temperature for Al-H and Al-D complexes, respectively. The absence of an anomalously large isotope shift is consistent with this excitation being due to an ordinary vibration rather than a tunneling splitting as is sometimes observed for hydrogen-containing complexes.

Formation of thermally stable high-resistivity AlGaAs by oxygen implantation

Abstract: Oxygen implantation into n+‐AlGaAs, followed by annealing above 600 °C, creates a deep acceptor level that compensates the shallow donors present in the material. Temperature‐dependent Hall measurements show that the resistivity of this compensated AlGaAs has a thermal activation energy of 0.49 eV, in contrast to a value of 0.79 eV for compensation caused by ion‐induced damage. The latter is stable only to 600 °C, whereas the chemically induced compensation in O‐implanted AlGaAs is stable above 950 °C.

Hydrogen motion in defect complexes: Reorientation kinetics of the B-H complex in silicon.

Abstract: On etudie le mouvement de l'hydrogene dans le complexe B-H dans le silicium. On applique une tension afin de produire une orientation preferentielle du complexe B-H a une temperature suffisamment haute pour que H puisse se deplacer sans le complexe (environ 60 K). On detecte l'alignement des complexes en comparant les forces d'absorption optique de la vibration d'etirement de H pour une lumiere polarisee parallele et perpendiculaire a l'axe de tension. A partir de la cinetique de decroissance d'alignement apres l'application de la tension, on montre que le mouvement de H d'un site de liaison centree a un autre autour de B est active thermiquement par une energie d'activation de 0•19 eV

Lattice location of deuterium interacting with the boron acceptor in silicon

Abstract: Etude de la localisation dans le reseau du deuterium, qui diffuse dans du silicium dope par du bore, par canalisation de particule

Ion implantation damage and annealing in InAs, GaSb, and GaP

Abstract: The characteristics of ion implantation induced damage in InAs, GaSb, and GaP, and its removal by rapid thermal annealing have been investigated by Rutherford backscattering and transmission electron microscopy. There is relatively poor regrowth of these materials if they were amorphized during the implantation, leaving significant densities of dislocation loops, microtwins, and in the case of GaSb, polycrystalline material. For implant doses below the amorphization threshold, rapid annealing produces good recovery of the lattice disorder, with backscattering yields similar to unimplanted material. The redistribution of the implanted acceptor Mg is quite marked in all three semiconductors, whereas the donor Si shows no measurable motion after annealing of InAs or GaP. In GaSb, however, where it appears to predominantly occupy the group III site, it shows redistribution similar to that of Mg.

Antiphase domains in GaAs grown by metalorganic chemical vapor deposition on silicon‐on‐insulator

Abstract: Distinct antiphase domain structures in GaAs epitaxial layers grown on a Si/SiO2/Si‐substrate structure by metalorganic chemical vapor deposition have been revealed by using a silicon etchant (HF/HNO3). The antiphase is characterized by the [011]‐oriented etching textures which rotate 90° between adjacent domains. The corresponding lattice rotation is further confirmed by a convergent beam electron diffraction technique. The size of the antiphase domains is found to increase with increasing film thickness and to grow upon annealing at temperatures above 700 °C. The maximum size of the domain, however, is found to be limited by the film thickness. The majority of the domain boundary lines revealed by chemical etching on the (100) surface do not correspond to any crystalline orientation. Only small segments are found to orient along [011], [010], [021], and, occasionally, [031] and [041] directions. Cross‐sectional transmission electron microscopy studies confirmed that the boundaries are generally in curve...

Structure of acceptor-hydrogen and donor-hydrogen complexes in silicon from uniaxial stress studies

Abstract: We report the results of a uniaxial stress study of the vibrational absorption due to hydrogen-passivated boron acceptors and arsenic donors in silicon. Under stress, the H-related vibrational bands shift and split in frequency. From the observed splittings and intensity ratios we determine that the symmetry of both centers is trigonal. For B-H we observe a large sensitivity to stress which we speculate is due to the tendency of H to move off the 〈111〉 axis of the complex under compression. The two vibrational bands of As-H are confirmed to be due to stretching and doubly degenerate wagging modes. Our results provide support for the structural model proposed by Johnson et al. [Phys. Rev. Lett. 56, 769 (1986)] for donor-H complexes in which the H is at the antibonding site of one of the donor's Si neighbors.

Thickness dependence of material quality in GaAs‐on‐Si grown by metalorganic chemical vapor deposition

Abstract: The evolution with increasing layer thickness of the structural and electrical properties of GaAs grown directly on Si or Si‐on‐insulator (SOI) by metalorganic chemical vapor deposition is reported. There is a substantial improvement in the surface morphology and near‐surface crystallinity of the GaAs in thicker films (≥1.5 μm). The implant activation efficiency of 60‐keV 29Si ions at a thickness of 4 μm is comparable to that seen in bulk GaAs. The deep level concentration is also observed to decrease with increasing layer thickness. Transmission electron microscopy reveals average defect densities near 108 cm−2 in films deposited either on misoriented or exact (100) Si, and in those grown on SOI.

Photoluminescence from annealed semi‐insulating GaAs crystals: The 1.360‐eV band

Abstract: We investigated the near‐band‐edge photoluminescence from semi‐insulating GaAs crystals after they were annealed either in the wafer form or in the bulk form. Our results, with respect to the uniformity achieved after annealing, are in agreement with previous studies. The 1.360‐eV emission band which is seen in annealed crystals and which has been taken to imply a VAs related rapid diffusion process as the mechanism responsible for the annealing‐induced uniformity, is shown not to be connected with it. We also cite evidence which questions the involvement of VAs in the band. From data in the literature we estimate the diffusion coefficient of VAs and find it to be too low to bring about bulk equilibrium and uniformity via vacancy diffusion from the surface at the annealing temperatures. We conclude that the local rearrangement of defects is a viable mechanism for producing uniformity during post‐growth annealing.

GaAs MESFETs, ring oscillators and divide-by-2 integrated circuits fabricated on MBE grown GaAs on Si substrates

Abstract: Using a very thin layer of GaAs (2.1 μm) on Si, we have fabricated GaAs MESFETs, 19 stage ring oscillators, and divide-by-2 frequency dividers with good yield. The MESFETs exhibited a maximum gm of 153 mS/mm. The DCFL 19 stage ring oscillators had a minimum propagation delay of 52ps/gate at a power dissipation of 1.3 mW/gate with a yield of 40%. The divide-by-2 circuits performed the frequency dividing operation up to 1.8 GHz.

Implantation tailoring of electrically active dopant profiles in GaAs

Abstract: A common problem with fabricating n‐type layers in semi‐insulating GaAs by ion implantation is the variation in the net activation efficiency on the substrate side of the implanted dopant profile. We compare two methods for modifying these doping profile tails in order to achieve uniform activation properties of implanted layers over large wafer areas. The two methods are compensation of an n‐type doping profile by a buried damage layer (oxygen or helium implants) or by coimplantation of an acceptor species (beryllium). Experimental results are shown both for n‐only and n+‐n profile modifications. The use of Be to form a buried p‐type layer has several advantages over the damage‐induced compensation.

Ion Implantation Damage and its Annealing Characteristics in an AlAs/GaAs Layer Structure

Abstract: The implantation of Ar + ions into AlAs/GaAs layered samples is shown to give very different damage structures in the two materials. While the GaAs is relatively easily amorphised, the AlAs is quite resistant to damage accumulation and remains crystalline for the ion doses employed in these investigations. The behaviour of the different damage structures when subjected to rapid thermal annealing treatments is described in some detail. It is demonstrated that differences in the initial damage state have a strong influence upon the nature of lattice defects produced by annealing.

Activation Characteristics of Implanted Dopants in InAs, GaSb and GaP After Rapid Thermal Annealing

Abstract: We have studied in some detail the activation of implanted Si and Mg ions in InAs, GaSb and GaP after rapid thermal annealing. Even at doses of 10 15 cm −2 , the activation percentage of Mg is relatively high after optimum anneals -80% in GaP, 55% in GaSb and 45% in InAs. There is considerable outdiffusion of Mg in all three semiconductors for extended heat treatments. The amphoteric species Si shows good activation (60% for 10 15 cm −2 dose) in InAs, a saturation electrically active concentration of ∼3 × 10 13 cm −2 in GaP, and very low electrical activity in GaSb. The regrowth and damage removal characteristics in the three materials are similar to those of GaAs and InP.

The role of crystal-growth properties on silicon implant activation processes for GaAs

Abstract: Crystal properties such as bulk resistivity, mobility, and dislocation density which influence ion‐implantation activation are reported for liquid‐encapsulated Czochralski, horizontal gradient freeze, and vertical gradient freeze semi‐insulating GaAs crystals. The liquid‐encapsulated Czochralski crystals used in this study include as‐grown, boule‐annealed, and indium‐alloyed GaAs. Wafer maps displaying the concentration and spatial distribution of neutral EL2 are presented for each crystal. Wafers from the various crystals were implanted with 29Si at a dose of 3×1012 ions/cm2 and an energy of 60 keV. Macroscopic variations in the donor distribution and peak carrier density demonstrate that point defects impact significantly the donor implant activation processes.

Behaviour of Implanted Hydrogen in Gallium Phosphide Single Crystals

Abstract: In this paper we report on the depth distributions of implanted hydrogen in GaP crystals and the subsequent changes produced by post- implantation furnace annealing. A sulfur doped n+ GaP wafer has been implanted with 333 keV protons to a fluence of 5E15/cm+2. A similar wafer was implanted with 350 keV deuterons to the same fluence. Portions of each wafer have been furnace annealed at temperatures up to 500°C. The implanted hydrogen and the dopant S atoms were then depth profiled using secondary ion mass spectrometry (SIMS). The measurements show that the redistribution of hydrogen begins with annealing at about 300°C and proceeds both towards the surface and deeper into the substrate. The overall behavior is similar to that found previously for hydrogen in GaAs. However, in GaP crystals this redistribution begins at a higher temperature and proceeds more slowly in the implanted region. Based on the SIMS profiles, diffusion coefficients for hydrogen migrating into substrate are obtained.

Implant Isolation Mechanisms in GaAs, AlGaAs, InP and InGaAs

Abstract: We have investigated the thermal stability of high resistivity regions introduced by ion bombardment of GaAs, AlGaAs, InP and InGaAs. For low doses in which the ion species density is below that of the doping density in the target material, we obtain the usual damage-related compensation in which deep levels created by the bombardment trap the charge carriers. By this method one creates material with resistivities around 108 Ω/□ (n- or p-type GaAs and AlGaAs, p-type InP), around 106 Ω/□ (n-type InP) or around 105 Ω/□ (n-type InGaAs or p-type InGaAs), with a return of the initial resistivity after elevated temperature annealing (∼600°C for GaAs and AIGaAs, ∼500°C for InP and InGaAs). The more interesting case is the use of higher dose implants of species which create chemical deep levels. This occurs for O in n-type AlGaAs where O creates a deep acceptor (Ec-0.49 eV), and Fe in n-type InP and InGaAs, where it is also a deep acceptor. When the concentration of these species exceeds the doping density in the material, the bombarded regions retain their high resistivity even after high temperature annealing (> 1000°C for GaAs and AIGaAs, >850°C for InP and InGaAs). The case of O in GaAs appears to represent a third mechanism; it creates thermally stable material only in the case of Be-doped GaAs, suggesting an ion-pairing reaction.

Temperature Dependence of Etch Rate and Residual Damage in Reactively Ion Etched GaAs and AlGaAs

Abstract: The etch rate of GaAs and AIGaAs during CC12F2:O2 reactive ion etching was measured over the temperature range 50–400oC. For GaAs, the etch rate increases super-linearly from ∼400A.min−1 to ∼3000Amin−1 over this temperature range for a 0.56 W.cm−2, 4 mTorr discharge with a 19:1 CC12F2:O2 mixture. The surface morphology of GaAs undergoes a smooth-to-rough transition near 150oC, and theresidual damage in the near-surface region appears to decrease with increasing etch temperature. The I-V characteristics of Schottky diodes fabricated on the etched surfaces show ideality factors of 1.001 for 150oC RIE, although these worsen because of thermal degradation of higher etching temperatures. From AES and XPS data the etched GaAs shows little contamination after etching. In contrast, little temperature dependence of the etch rate of AIGaAs is observed using CC12F2:O2, although once again there is surface degradation for etching temperatures above 150oC.

Material and Device Properties of 3” Diameter GaAs-on-Si with Buried P-type Layers

Abstract: Two problems facing MOCVD grown GaAs-on-Si are firstly, scale up to 3” and greater wafer diameter with acceptably uniform layer thicknesses and electrical and optical properties, and secondly the achievement of adequate device isolation through the use of buffer layers of low doping density (≤1014 cm−3). We have investigated the thickness uniformity and 300K photoluminescence intensity of 3” O, MOCVD grown GaAs layers on Si substrates by whole wafer mapping of these parameters, and correlate the variations found with the gas flow direction during deposition of the GaAs. We have overcome the high background doping densities (n =5−20 × 1015 cm2) in the material by a buried Be implant (1−5 × 1012 at 120 keV) followed by 850°C, 3 sec annealing. This provides adequate isolation for MESFETS and we fabricated such devices with gm’s of 160-175 mS mm−1 using our standard process. These values are similar to homoepitaxial MESFETS fabricated in the same way.

Activation and Interdiffusion Characteristics in Implanted GaAs-AlGaAs Heterostructures on Si

Abstract: The activation kinetics and diffusion behaviour of implanted Be and Si in two different types of MOCVD-grown GaAs-AlGaAs heterostructures on Si substrates were examined by electrochemical C-V profiling, secondary ion mass spectrometry and sheet resistivity measurements. The implanted Be displays a thermal activation energy of 0.70 eV and Si a thermal activation energy of 0.53 eV in heteroepitaxial material, similar to the comparable cases in homoepitaxial GaAs. In addition, there is no evidence for enhanced diffusivity of either species, at least for implants located away from the heterointerface. The remnant lattice disorder in the heterostructures caused by implantation and annealing is negligible compared to the as-grown disorder, as revealed by transmission electron microscopy.

Ion Beam Induced Intermixing of Wsi0.45 on GaAs

Abstract: The systematics of ion beam induced intermixing of WSio.45 on GaAs have been studied after through-implantation of Si or O in the dose range 1013 - 5 x 1016 cm-2. SIMS profiling shows significant knock-on of Si and W into the GaAs at the high dose range in accordance with Monte Carlo simulations, but there is virtually no electrical activation (≤0.1%) of this Si after normal implant annealing (900*C, 10 sec). This appears to be a result of the high level of disorder near the metal-semiconductor interface, which is not repaired by annealing. This damage consists primarily of dislocation loops extending a few hundred angstroms below the end of range of the implanted ions. Extrapolation of the ion doses used in this work to the usual doses used in GaAs device fabrication would imply that ion-induced intermixing of WSix will not be significant in through-implantation processes.

Growth and Characterization of GaAs-Based Heterostructures on Si By Mocvd

Abstract: Several different types of GaAs-AlGaAs heterostructures were grown on Si substrates by MOCVD. The defect density in as-grown samples (~10 8 cm −2 ) was similar to that of GaAs layers grown directly on Si, and the crystalline quality of the material was observed to improve slightly with post-growth annealing at 900°C. We examined the diffusion of both Si and Zn dopants during this type of annealing and found only a small amount of redistribution of both species. Laser annealing of GaAs-on-Si was also examined as a method of reducing the defect density in the material - we observed substantial improvements in surface quality, but no change in sub-surface crystalline quality.