On the nature of the oxygen-related defect in aluminum nitride

1990 ◽  
Vol 5 (8) ◽  
pp. 1763-1773 ◽  
Author(s):  
J. H. Harris ◽  
R. A. Youngman ◽  
R. G. Teller
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Nitride ◽  
Lattice Parameter ◽  
Extended Defects ◽  
Inversion Domain ◽  
Transmission Electron ◽  
Oxygen Related Defect ◽  
Diffraction Lattice ◽  
Related Defect ◽  
Oxygen Concentrations

The oxygen-related defect in an aluminum nitride (AIN) single crystal and in polycrystalline ceramics is investigated utilizing photoluminescence spectroscopy, thermal conductivity measurements, x-ray diffraction lattice parameter measurements, and transmission electron microscopy. The results of these measurements indicate that at oxygen concentrations near 0.75 at.%, a transition in the oxygen accommodating defect occurs. On both sides of this transition, simple structural models for the oxygen defect are proposed and shown to be in good agreement with the thermal conductivity and lattice parameter measurements, and to be consistent with the formation of various extended defects (e.g., inversion domain boundaries) at higher oxygen concentrations.

The Oxygen-Related Defect in Aluminum Nitride Ceramics: a Thermal Conduction Limiting Defect in a Technologically Important Material

1993 ◽  
Vol 323 ◽  
Author(s):  
Jonathan H. Harris ◽  
Robert A. Youngman ◽  
Rudy Enck
Keyword(s):  
Thermal Conductivity ◽  
Integrated Circuits ◽  
Aluminum Nitride ◽  
Thermal Conduction ◽  
Electronic Packages ◽  
Electrical Measurements ◽  
Oxygen Related Defect ◽  
New Material ◽  
Related Defect ◽  
High Concentrations

AbstractAluminum nitride (AlN) sintered ceramics are a critical new material for electronic packaging applications, principally because of AlN's high thermal conductivity and close thermal expansion match to silicon. AlN is expected to play a key role in the next generation of high powder electronic packages, in applications ranging from high power discrete component substrates to co-fired, multilayer packages for integrated circuits. In the following paper, a detailed picture of the oxygen-related defect in AlN ceramics is presented. This impurity is of critical technological importance, because vacancies associated with oxygen severely limit thermal conduction when present in high concentrations. The results of thermal conductivity measurements, luminescence studies, optical absorption experiments, photo-induced absorption studies and electrical measurements on both ceramic and single crystal samples will be presented in order to understand the detailed nature of this defect and to model its control over a number of important technological properties.

Oxygen incorporation in aluminum nitride via extended defects: Part III. Reevaluation of the polytypoid structure in the aluminum nitride-aluminum oxide binary system

1995 ◽  
Vol 10 (10) ◽  
pp. 2573-2585 ◽  
Author(s):  
Alistair D. Westwoord ◽  
Robert A. Youngman ◽  
Martha R. McCartney ◽  
Alasiair N. Cormack ◽  
Michael R. Notis
Keyword(s):  
Aluminum Nitride ◽  
Stacking Faults ◽  
Structural Rearrangement ◽  
Extended Defects ◽  
Structural Elements ◽  
Inversion Domain ◽  
Transmission Electron ◽  
New Variant ◽  
Domain Boundaries ◽  
Inversion Domain Boundaries

This paper extends the concepts that were developed to explain the structural rearrangement of the wurtzite AlN lattice due to incorporation of small amounts of oxygen, and to directly use them to assist in understanding the polytypoid structures. Conventional and high-resolution transmission electron microscopy, specific electron diffraction experiments, and atomistic computer simulations have been used to investigate the structural nature of the polytypoids. The experimental observations provide compelling evidence that polytypoid structures are not arrays of stacking faults, but are rather arrays of inversion domain boundaries (IDB's). A new model for the polytypoid structure is proposed with the basic repeat structural unit consisting of a planar IDB-P and a corrugated IDB. This model shares common structural elements with the model proposed by Thompson, even though in his model the polytypoids were described as consisting of stacking faults. Small additions (≃ 1000 ppm) of silicon were observed to have a dramatic effect on the polytypoid structure. First, it appears that the addition of Si causes the creation of a new variant of the planar IDB (termed IDB-P'), different from the IDB-P defect observed in the AlN-Al2O3 polytypoids; second, the addition of Si influences the structure of the corrugated IDB, such that it appears to become planar.

Planar and Curved Defects in Aluminum Nitride: Their Microstructure and Microchemistry

1989 ◽  
Vol 167 ◽  
Author(s):  
Alistair D. Westwood ◽  
Michael R. Notis
Keyword(s):  
Electron Microscopy ◽  
Aluminum Nitride ◽  
Analytical Electron Microscopy ◽  
Microchemical Analysis ◽  
Inversion Domain ◽  
Transmission Electron ◽  
Proposed Model ◽  
Domain Boundaries ◽  
Convergent Beam ◽  
Inversion Domain Boundaries

AbstractThe microstructure and microchemistry of planar and curved defects in Aluminum Nitride (AIN) has been investigated using Conventional Transmission Electron Microscopy (CTEM), Convergent Beam Electron Diffraction (CBED), and Analytical Electron Microscopy (AEM) techniques. Both defect morphologies were identified as Inversion Domain Boundaries (IDB). Microchemical analysis revealed oxygen segregation to the planar faults; when present on the curved defects, oxygen was at a lower concentration than in the planar defect case. Annealing experiments on defect containing AIN support our microchemical analysis of oxygen segregation. A proposed model for the formation of these two types of boundaries is presented.

scholarly journals Extended Defects in GaN: a Theoretical Study

1999 ◽  
Vol 4 (S1) ◽  
pp. 250-256 ◽  
Author(s):  
J. Elsner ◽  
Th. Frauenheim ◽  
M. Haugk ◽  
R. Gutierrez ◽  
R. Jones ◽  
...  
Keyword(s):  
Density Functional ◽  
Extended Defects ◽  
Functional Theory ◽  
Screw Dislocations ◽  
Defect Complexes ◽  
Oxygen Related Defect ◽  
Domain Boundaries ◽  
Related Defect ◽  
Image Position ◽  
Edge Dislocations

We present density–functional theory studies for a variety of surfaces and extended defects in GaN. According to previous theoretical studies1{100} type surfaces are electrically inactive. They play an important role in GaN since similar configurations occur at open–core screw dislocations and nanopipes as well as at the core of threading edge dislocations. Domain boundaries are found to consist of four–fold coordinated atoms and are also found to be electrically inactive. Thus, except for full–core screw dislocations which possess heavily strained bonds all investigated extended defects do not induce deep states into the band–gap. However, electrically active impurities in particular gallium vacancies and oxygen related defect complexes are found to be trapped at the stress field of the extended defects.

Application of AEM to chemical and structural characterization of the AlN-Al2O3 and AlN-Al2O3-SiO2 Systems

1995 ◽  
Vol 53 ◽  
pp. 318-319
Author(s):  
A. D. Westwood
Keyword(s):  
Thermal Conductivity ◽  
Defect Formation ◽  
Prototype System ◽  
Extended Defects ◽  
Inversion Domain ◽  
Domain Boundaries ◽  
Properties Of Materials ◽  
Inversion Domain Boundaries

The thermal, electronic and mechanical properties of aluminum nitride (A1N) make it an attractive material to a number of technologically important areas; microelectronic packaging, high temperature semiconductors, opto-electronic and piezoelectric devices and structural ceramics. It is well established that the concentration and distribution of impurities can control the macroscopic properties of materials. A1N is a classic example, with oxygen (O) being the dominant controlling impurity. The role of O in point defect formation and its detrimental effect on thermal conductivity was first documented by Slack. Oxygen has subsequently been shown to cause the formation of two-dimensional extended defects of which two variants exist, planar and curved. Both defects have been identified as O-rich inversion domain boundaries (IDB´s) (Fig.l). Because of the controlling influence that O has on thermal conductivity, it is important to fully understand the defect structures and chemistries that exist as a result of O incorporation. A1N-A12O3 is a prototype system for understanding the role that non-stoichiometry (impurities) plays in IDB formation.

Oxygen incorporation in aluminum nitride via extended defects: Part I. Refinement of the structural model for the planar inversion domain boundary

1995 ◽  
Vol 10 (5) ◽  
pp. 1270-1286 ◽  
Author(s):  
Alistair D. Westwood ◽  
Robert A. Youngman ◽  
Martha R. McCartney ◽  
Alastair N. Cormack ◽  
Michael R. Notis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Nitride ◽  
Basal Plane ◽  
Displacement Vector ◽  
Domain Boundary ◽  
Analytical Electron Microscopy ◽  
Interfacial Structure ◽  
Inversion Domain ◽  
Transmission Electron

The model proposed by Harris et al. [J. Mater. Res. 5, 1763–1773 (1990)], describing planar inversion domain boundaries in aluminum nitride, consists of a basal plane of aluminum atoms octahedrally coordinated with respect to oxygen, and with a translation of R = 1/3〈1011〉. This thin sandwich is inserted onto the basal plane of the wurtzite structure of aluminum nitride. This model does not take into consideration any interfacial relaxation phenomena, and is arguably electrically unstable. Therefore, this paper presents a refinement of the model of Harris et al., by incorporating the structural relaxations arising from modifications in local chemistry. The interfacial structure was investigated through the use of conventional transmission electron microscopy, convergent electron diffraction, high resolution transmission electron microscopy, analytical electron microscopy, and atomistic computer simulations. The refined planar inversion domain boundary model is closely based on the original model of Harris et al.; however, the local chemistry is changed, with every fourth oxygen being replaced by a nitrogen. Atomistic computer simulation of these defects, using a classical Born model of ionic solids, verified the stability of these defects as arising from the adjustment in the local chemistry. The resulting structural relaxations take the form of a 0.3 mrad twist parallel to the interface, a contraction of the basal planes adjacent to the planar inversion domain boundary, and an expansion of the c-axis component of the displacement vector; the new displacement vector across the interface is R = 1.3〈1010〉 + ∊〈0001〉, where ∊meas = 0.387 and ∊calc = 0.394.

Extended Defects in GaN: a Theoretical Study

1998 ◽  
Vol 537 ◽  
Author(s):  
J. Eisner ◽  
Th. Frauenheim ◽  
M. Haugk ◽  
R. Gutierrez ◽  
R. Jones ◽  
...  
Keyword(s):  
Density Functional ◽  
Extended Defects ◽  
Functional Theory ◽  
Screw Dislocations ◽  
Defect Complexes ◽  
Oxygen Related Defect ◽  
Domain Boundaries ◽  
Related Defect ◽  
Edge Dislocations ◽  
Open Core

AbstractWe present density-functional theory studies for a variety of surfaces and extended defects in GaN. According to previous theoretical studies {1010} type surfaces are electrically inactive. They play an important role in GaN since similar configurations occur at open-core screw dislocations and nanopipes as well as at the core of threading edge dislocations. Domain boundaries are found to consist of four-fold coordinated atoms and are also found to be electrically inactive. Thus, except for full-core screw dislocations which possess heavily strained bonds all investigated extended defects do not induce deep states into the band-gap. However, electrically active impurities in particular gallium vacancies and oxygen related defect complexes are found to be trapped at the stress field of the extended defects.

Oxygen incorporation in aluminum nitride via extended defects: Part II. Structure of curved inversion domain boundaries and defect formation

1995 ◽  
Vol 10 (5) ◽  
pp. 1287-1300 ◽  
Author(s):  
Alistair D. Westwood ◽  
Robert A. Youngman ◽  
Martha R. McCartney ◽  
Alastair N. Cormack ◽  
Michael R. Notis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Nitride ◽  
Displacement Vector ◽  
Interfacial Structure ◽  
Formation Mechanisms ◽  
Inversion Domain ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Inversion Domain Boundaries

Three distinct morphologies of curved (curved, facetted, and corrugated) inversion domain boundaries (IDB's), observed in aluminum nitride, have been investigated using conventional transmission electron microscopy, convergent beam electron diffraction, high-resolution transmission electron microscopy, analytical electron microscopy, and atomistic computer simulations. The interfacial structure and chemistry of the curved and facetted defects have been studied, and based upon the experimental evidence, a single model has been proposed for the curved IDB which is consistent with all three observed morphologies. The interface model comprises a continuous nitrogen sublattice, with the aluminum sublattice being displaced across a {1011} plane, and having a displacement vector R = 0.23〈0001〉. This displacement translates the aluminum sublattice from upwardly pointing to downwardly pointing tetrahedral sites, or vice versa, in the wurtzite structure. The measured value of the displacement vector is between 0.05〈0001〉 and 0.43〈0001〉; the variation is believed to be due to local changes in chemistry. This is supported by atomistic calculations which indicate that the interface is most stable when both aluminum vacancies and oxygen ions are present at the interface, and that the interface energy is independent of displacement vector in the range of 0.05〈0001〉 to 0.35〈0001〉. The curved IDB's form as a result of nonstoichiometry within the crystal. The choice of curved IDB morphology is believed to be controlled by local changes in chemistry, nonstoichiometry at the interface, and proximity to other planar IDB's (the last reason is explained in Part III). A number of possible formation mechanisms are discussed for both planar and curved IDB's. The Burgers vector for the dislocation present at the intersection of the planar and curved IDB's was determined to be b = 1/3〈1010〉 + t〈0001〉, where tmeas = 0.157 and tcalc = 0.164.

Structural and electronic properties of defects in semiconductors

1995 ◽  
Vol 53 ◽  
pp. 4-5
Author(s):  
J.L. Batstone
Keyword(s):  
Semiconductor Device ◽  
Chemical Vapor ◽  
Misfit Strain ◽  
Organic Chemical ◽  
Extended Defects ◽  
Transmission Electron ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Metal Organic ◽  
Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

CBED analysis of impurity distributions in AlN

1990 ◽  
Vol 48 (4) ◽  
pp. 214-215
Author(s):  
Daniel Callahan ◽  
G. Thomas
Keyword(s):  
Aluminum Nitride ◽  
Bulk Material ◽  
Strong Dependence ◽  
Lattice Parameter ◽  
Promising Technique ◽  
Nitride Ceramics ◽  
Surface Phases ◽  
Convergent Beam ◽  
Oxygen Impurities

Oxygen impurities may significantly influence the properties of nitride ceramics with a strong dependence on the microstructural distribution of the impurity. For example, amorphous oxygen-rich grain boundary phases are well-known to cause high-temperature mechanical strength degradation in silicon nitride whereas solutionized oxygen is known to decrease the thermal conductivity of aluminum nitride. Microanalytical characterization of these impurities by spectral methods in the AEM is complicated by reactions which form oxygen-rich surface phases not representative of the bulk material. Furthermore, the impurity concentrations found in higher quality ceramics may be too low to measure by EDS or PEELS. Consequently an alternate method for the characterization of impurities in these ceramics has been investigated.Convergent beam electron diffraction (CBED) is a promising technique for the study of impurity distributions in aluminum nitride ceramics. Oxygen is known to enter into stoichiometric solutions with AIN with a consequent decrease in lattice parameter.

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