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Study of decoration microdefects in lec-grown Si-doped GaAs crystals by selective photoetching and laser scattering tomography
Journal of Crystal Growth 106 (1990) 175—180 North-Holland
175
STUDY OF DECORATION MICRODEFECFS IN LEC-GROWN Si-DOPED GaAs CRYSTALS BY SELECI1VE PHOTOETCHING AND LASER SCATTERING TOMOGRAPHY J.L. WEYHER MASPEC-CNR, Via Chiavari 18/A, 1-43100 Parma Italy
P. GALL Centre d’Electronique de Monipellier, F-34060 Monipellier, France
G. FRIGERIO Enichem SpA, RJSV-MTEJ, 1-20100 Milano, Italy
and L. ZANOTFI MASPEC-CNR~Via Chiavari 18/A, 1-43100 Parma Italy Received 15 February 1990; manuscript received in final form 24 April 1990
The status of decoration microdefects along the grown-in dislocations was studied in Si-doped LEC GaAs by means of selective DSL photoetching and laser scattering tomography (LST). It will be shown that the existence and type of microdefects in GaAs 3 is strongly dependent on the melt stoichiometry. In As-rich material numerous arsenic doped with silicon to give n ~10I8 cm decoration precipitates are present. In Ga-rich material complex decoration defects are formed while in stoichiometric samples no decoration effect could be recognized neither by DSL photoetching nor by LST. In addition in the latter material the presence of very fine matrix microdefects is evidenced by DSL and LST.
The influence of chemical composition (deviation from stoichiometry) on structure and electrical parameters of undoped, LEC-grown GaAs crystals is already well recognized and documented, see for instance refs. [1—3].Recent studies performed on n-type, Si-doped LEC GaAs have also shown essential dependence of electrical [4] and structural [5,6] properties of crystals upon the liquid phase composition. In Si-doped GaAs, however, the amphoteric nature of silicon, contamination with carbon and boron and possible interaction between resultant defects, make it more difficult to interpret the structural and electrical features of crystals grown from non-stoichiometnc melts. 0022-0248/90/$03.50 © 1990
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In a recent paper [6] we have shown the variable status of the grown-in defects and associated microdefects in the central part of three ingots grown in As-rich, stoichiometric and Ga-rich conditions. In this communication additional results are presented on the nature, degree and type of decoration of the grown-in dislocations in the same crystals. Two complementary methods were used to locate and study these defects, namely: DSL photoetching [7] and laser scattering tomography (LST) [8], the latter technique being particularly suitable to study the spatial distribution of decorating particles (DPs). The experimental conditions were the same as described previously in ref. [6] for DSL photoetching and in ref. [9] for
Elsevier Science Publishers B.V. (North-Holland)
176
J.L. Wevher et al.
/ Decoration microdefects in LEC-grown Si-doped GaAs
LST. The same central part of the GaAs wafers were subjected to LST and subsequently to DSL photoetching in order to obtain direct calibration, Sequential photoetching was also used to study the status of some defects in depth of the wafers. All crystals had carrier concentration n = (1—2) x 10i~cm3 i.e. were grown under the conditions of doping-related reduced dislocation density.
In the central part of crystal No. 1 (As-rich melt) dislocations almost parallel to the (100) surface and arranged in an orthogonal pattern are prevailing (fig. la). Among them some individual or clustered defects are present, perpendicular or inclined versus the surface. All of these dislocations are decorated by the As-type precipitates, what is obvious after DSL photoetching: numer-
I
___________
A
“7 ~
t~
Fig. 1. Dislocations and decoration precipitates in Si-doped, As-rich GaAs crystal: (a) network of grown-in dislocations and (b) As precipitates-related shallow pits after DSL photoetching; (c) LST image of decoration precipitates.
J.L Weyher es al.
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Decoration microdefecisinLEC-grown Si-doped GaAs
ous shallow pits are present along the dislocationrelated etch hillocks, as shown in fig. lb. It is evident from previous calibrations of the AB and DSL etching methods by TEM analysis that there is a direct correspondence between shallow pits and precipitates consisting of elemental hexagonal arsenic [10—12].LST investigation of the same area shows decorating particles, clearly along mdividual dislocations (fig. lc). The density of these particles is similar to the density of shallow pits on dislocations revealed by photoetching (compare figs. lb and lc). The overall defect structure of crystal No. 2 (Ga-rich melt) is similar to that of crystal No. 1, but the density of dislocations is remerkably lower [6]. Essential difference is observed in the nature of decorating microdefects: majority of them cause formation of small hillocks (H) situated along the extended ridges related to the Cottrell atmospheres (details on the nature of these atmospheres are given in ref. [13]), as shown in fig. 2a for a grown-in dislocation parallel to the surface. A similar situation is observed on clusters of dislocations which are perpendicular to the surface. The morphology of hillocks does not change after deep sequential photoetching, which excludes the possible presence of pure As precipitates as the constituents of decorating microdefects. Therefore, these are either precipitates resistant to the DS etchant or other defects such as entangled dislocation loops. Recent TEM study of similar GaAs crystals [5] suggests the presence of more complex polycrystalline inclusions containing different elements. However, only direct calibration
177
of the DSL etch features with TEM could help to define the exact nature of these defects. It is here worth noting that occasionally the As-related shallow pits (P) are also formed, see fig. 2a. Though the nature of decorating particles is evidently different in As- and Ga-rich crystals, the LST images are similar (compare figs. lc and 2b). From the LST it can be concluded that at least the size (i.e. the yield of scattering) of DPs in Ga-rich material is of the same order of magnitude as the size of As precipitates in As-rich GaAs. In stoichiometric GaAs (crystal No. 3), two types of dislocations are present, namely grown-in (G) and grown-in, later moved by stresses (G-S), notation after ref. [14]. The majority of the G-dislocations are perpendicular to the (100) surface, some of them forming low-angle grain boundaries (LAGB) which are known to have a (100) direction of the dislocation lines [11,15]. Examples of both types are shown in figs. 3a and 3b. Both the crystallographic orientation and the fact that the same arrays of these dislocations were observed in a number of wafers along the axis of ingot suggest that they originate from the seed. Such dislocations called “E” were already shown by X-ray topography in (110) longitudinal sections of Sidoped GaAs crystals [16]. Previously we reported the presence of not typical shallow pits on all G and G-S dislocation-related etch hillocks (see fig 4H in ref. [6]). However, further detailed optical study after shallow and deep DSL photoetching performed on wafers from the same GaAs ingot did not reveal the presence of any pits. LST examination of large central part of the wafers which
Fig. 2. Dislocations and decoration microdetects in Si-doped. (ia-nch (iaAs crystal: (a) etch hillocks (H) and shallow pit (t’) alter DSL photoetching; (b) LST image of decoration microdefects.
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/ Decoration microdefects in LEC-grown Si-doped GaAs
were subsequently photoetched did not disclose any decoration particles either see fig 3c. At the same time both DSL and LST showed the presence of some decoration precipitates close to the edges of the examined wafers. Therefore we condude that al~G and G-S dislocations in the central part of the GaAs ingot grown from stoichiometric melt are free of any decoration particles. Previously recorded pits after DSL photoetching might have been caused rather by the chemistry-related factors of the Cr03—HF—H20 etching system, than —
by the presence of any structural features along the dislocation lines. Additional peculiar features, observed both after DSL and LST examination, are the overall
microroughness (M in figs. 3a and 3b) and the background scattering on the dislocation free matrix, respectively. The latter effect is well seen when the laser beam is cut off for some time, as shown in fig. 4. Similar features were already observed in Si-doped crystals from another manufacturer [17]. Both experimental facts suggest the presence in the matrix of nanometer-scale defects in very high density, uniformly distributed in the micro-scale. These might be small dislocation loops or precipitates, such as observed by HVTEM in the matrix of the dislocation cells in SI undoped GaAs crystals [18]. Additional arguments indicating the presence of numerous dislocation loops have been obtained from DSL/TEM
LAGB
Fig. 3. Dislocations in Si-doped GaAs grown from stoichiometric melt. (a), (b) Etch hiflocks after DSL photoetching. (c) LST image of the area covering fragments shown in (a) and (b). For description of abbreviations, see text.
J.L Weyher et al.
/
Decoration microdefects in LEC-grown Si-doped GaAs
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formed. Therefore it can be suggested that for stoichiometric melt and using dislocation free seed it is possible to grow GaAs with essentially reduced density of grown-in dislocations. (4) It has been discovered by the LST method that in all examined samples there exist submicron matrix defects. These are most probably extrinsic dislocation loops which influence the morphology of GaAs surface after DSL photoetching (microroughness).
~
Fig. 4. Background of the matrix in the GaAs crystal No. 3 evidenced by the cutting-off of the laser beam.
References study of SI GaAs after Si ion implantation followed by rapid thermal annealing. The overall microroughness which appears after DSL photoetching of implanted material [19] is now well correlated by TEM with ioops of interstitial type [20]. The alternative possibility of the existence of small As precipitates in the matrix of our Si-doped GaAs has to be rather exluded because neither shallow pits nor denuded zones around dislocations are present (see figs. 3a and 3b) as was reported in ref. [21].
Conclusions (1) In LEC-grown GaAs doped with Si to the level of carrier concentration fl = (1—2) X 1018 cm the composition of melt is decisive for the formation of microdefects and density of grown-in dislocations in the central part of the ingots. (2) The decoration microdefects are: (1) As precipitates (in GaAs grown from As-rich melt) and (2) complex microdefects such as entangled dislocation loops and/or precipitates resistant to the DS etchant (in GaAs grown from Ga-rich melt). No decoration microdefects recognizable by the DSL photoetching and LST method are present in the material grown from stoichiometric melt. (3) The density of grown-in dislocations is evidently related to the presence and type of decorating microdefects, being the highest for As-rich growth conditions, i.e. when As precipitates are ~,
[1] D.E. Holmes, R.T. Chen, K.R. Elliott, C.G. Kirkpatrick and Ph. Won Yu. IEEE Trans. Electron Devices, ED-29 (1982) 1045. [2] T. Inada, T. Sato. K. Ishida,T. Fukuda and S. Takahashi, J. Electron. Mater. 15 (1986) 169. [3] K. Terashima, in:, Semi-Insulating Ill—V Materials, Malmo, 1988, Eds. G. Grossmann and L. Ledebo (Huger, Bristol, 1989) p. 413. [4] R. Forn~. J. Crystal Growth 94 (1989) 433. [5] R. Fornari, C. Fngeri and R. Gleichmann, J. Electron. Mater. 18 (1989) 189. [6] G. Frigerio. C. Mucchino, J.L. Weyher, L. Zanotti and C. Paorici, J. Crystal Growth 99 (1990) 685. [7] J.L. Weyher and J. van de Yen, J. Crystal Growth 63 (1983) 285. [8] T. Ogawa, in: Defect Recognition and Image Processing m Ill—V Compounds (DRIP), Ed. J.P. Fillard (Elsevier, p. J.L. 1. Weyher, M. Asgarina and P.C. [9] Amsterdam, J.P. Fillard, 1985) P. Gall, Montgomery, in: Semi-Insulating Ill—V Materials, Malmo, 1988, Eds. G. Grossmann and L. Ledebo (Hilger, Bristol, 1989) p. 537. [101A.G. Cuffis, P.D. Augustus and DJ. Stirland, J. Appi. Phys. 51(1980) 2556. [11] J.L. Weyher and J. van de Ven, J. Crystal Growth 78 (1986) 191. [12] ED. Bourret, A.G. Elliot, B.-T. Lee and J.M. Jaldevic, in: Defect Recognition and Image Processing in Ill—V Compounds II (DRIP II), Ed. E.R. Weber (Elsevier, Amsterdam, 1987) p. 95. [13] C. Frigen and J.L. Weyher, J. AppI. Phys. (1989) 4646. [14] J.L. Weyher and L.J. Giling, in: Defect Recognition and Image Processing in Ill—V Compounds (DRIP), Ed. J.P. Fillard (Elsevier, Amsterdam, 1985) p. 63. [15] Phys. Chem. (1962)G.1353. [16] D.B. A.G. Holt, Elliot,J.Chia-Li Wei, Solids R. Farraro, Woolhouse, M. Scott and R. Hiskes, J. Crystal Growth 70 (1984) 169. [17] J.L. Weyher and P. Gall, CEM-USTL Report for Wacker Chemitronic GmbH, Montpellier, March 1988.
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/ Decoration microdefects in LEC-grown Si-doped GaAs
[18] F.A. Ponce, F.-C. Wang and R. Hiskes, in: Semi-Insulating Ill-V Materials, Kah-nee-ta, Warm Springs, OR, 1984, Eds. D.C. Look and J.S. Blakemore (Shiva, Nantwich, 1984) p. 68. [19] M. Dc Potter, W. Dc Raedt, M. Van Hove, M. Van
Rossum and J.L. Weyher, in: Proc. E-MRS Meeting, 1987, Vol. XVI, Eds. Y.I. Nissim and P.A. Glasow (Les Editions de Physique, Paris, 1987) p. 227. [20] J.L. Weyher and C. Frigeri, unpublished results. [21] K. Yamada and J. Osaka, J. AppI. Phys. (1988) 2609.
175
STUDY OF DECORATION MICRODEFECFS IN LEC-GROWN Si-DOPED GaAs CRYSTALS BY SELECI1VE PHOTOETCHING AND LASER SCATTERING TOMOGRAPHY J.L. WEYHER MASPEC-CNR, Via Chiavari 18/A, 1-43100 Parma Italy
P. GALL Centre d’Electronique de Monipellier, F-34060 Monipellier, France
G. FRIGERIO Enichem SpA, RJSV-MTEJ, 1-20100 Milano, Italy
and L. ZANOTFI MASPEC-CNR~Via Chiavari 18/A, 1-43100 Parma Italy Received 15 February 1990; manuscript received in final form 24 April 1990
The status of decoration microdefects along the grown-in dislocations was studied in Si-doped LEC GaAs by means of selective DSL photoetching and laser scattering tomography (LST). It will be shown that the existence and type of microdefects in GaAs 3 is strongly dependent on the melt stoichiometry. In As-rich material numerous arsenic doped with silicon to give n ~10I8 cm decoration precipitates are present. In Ga-rich material complex decoration defects are formed while in stoichiometric samples no decoration effect could be recognized neither by DSL photoetching nor by LST. In addition in the latter material the presence of very fine matrix microdefects is evidenced by DSL and LST.
The influence of chemical composition (deviation from stoichiometry) on structure and electrical parameters of undoped, LEC-grown GaAs crystals is already well recognized and documented, see for instance refs. [1—3].Recent studies performed on n-type, Si-doped LEC GaAs have also shown essential dependence of electrical [4] and structural [5,6] properties of crystals upon the liquid phase composition. In Si-doped GaAs, however, the amphoteric nature of silicon, contamination with carbon and boron and possible interaction between resultant defects, make it more difficult to interpret the structural and electrical features of crystals grown from non-stoichiometnc melts. 0022-0248/90/$03.50 © 1990
—
In a recent paper [6] we have shown the variable status of the grown-in defects and associated microdefects in the central part of three ingots grown in As-rich, stoichiometric and Ga-rich conditions. In this communication additional results are presented on the nature, degree and type of decoration of the grown-in dislocations in the same crystals. Two complementary methods were used to locate and study these defects, namely: DSL photoetching [7] and laser scattering tomography (LST) [8], the latter technique being particularly suitable to study the spatial distribution of decorating particles (DPs). The experimental conditions were the same as described previously in ref. [6] for DSL photoetching and in ref. [9] for
Elsevier Science Publishers B.V. (North-Holland)
176
J.L. Wevher et al.
/ Decoration microdefects in LEC-grown Si-doped GaAs
LST. The same central part of the GaAs wafers were subjected to LST and subsequently to DSL photoetching in order to obtain direct calibration, Sequential photoetching was also used to study the status of some defects in depth of the wafers. All crystals had carrier concentration n = (1—2) x 10i~cm3 i.e. were grown under the conditions of doping-related reduced dislocation density.
In the central part of crystal No. 1 (As-rich melt) dislocations almost parallel to the (100) surface and arranged in an orthogonal pattern are prevailing (fig. la). Among them some individual or clustered defects are present, perpendicular or inclined versus the surface. All of these dislocations are decorated by the As-type precipitates, what is obvious after DSL photoetching: numer-
I
___________
A
“7 ~
t~
Fig. 1. Dislocations and decoration precipitates in Si-doped, As-rich GaAs crystal: (a) network of grown-in dislocations and (b) As precipitates-related shallow pits after DSL photoetching; (c) LST image of decoration precipitates.
J.L Weyher es al.
/
Decoration microdefecisinLEC-grown Si-doped GaAs
ous shallow pits are present along the dislocationrelated etch hillocks, as shown in fig. lb. It is evident from previous calibrations of the AB and DSL etching methods by TEM analysis that there is a direct correspondence between shallow pits and precipitates consisting of elemental hexagonal arsenic [10—12].LST investigation of the same area shows decorating particles, clearly along mdividual dislocations (fig. lc). The density of these particles is similar to the density of shallow pits on dislocations revealed by photoetching (compare figs. lb and lc). The overall defect structure of crystal No. 2 (Ga-rich melt) is similar to that of crystal No. 1, but the density of dislocations is remerkably lower [6]. Essential difference is observed in the nature of decorating microdefects: majority of them cause formation of small hillocks (H) situated along the extended ridges related to the Cottrell atmospheres (details on the nature of these atmospheres are given in ref. [13]), as shown in fig. 2a for a grown-in dislocation parallel to the surface. A similar situation is observed on clusters of dislocations which are perpendicular to the surface. The morphology of hillocks does not change after deep sequential photoetching, which excludes the possible presence of pure As precipitates as the constituents of decorating microdefects. Therefore, these are either precipitates resistant to the DS etchant or other defects such as entangled dislocation loops. Recent TEM study of similar GaAs crystals [5] suggests the presence of more complex polycrystalline inclusions containing different elements. However, only direct calibration
177
of the DSL etch features with TEM could help to define the exact nature of these defects. It is here worth noting that occasionally the As-related shallow pits (P) are also formed, see fig. 2a. Though the nature of decorating particles is evidently different in As- and Ga-rich crystals, the LST images are similar (compare figs. lc and 2b). From the LST it can be concluded that at least the size (i.e. the yield of scattering) of DPs in Ga-rich material is of the same order of magnitude as the size of As precipitates in As-rich GaAs. In stoichiometric GaAs (crystal No. 3), two types of dislocations are present, namely grown-in (G) and grown-in, later moved by stresses (G-S), notation after ref. [14]. The majority of the G-dislocations are perpendicular to the (100) surface, some of them forming low-angle grain boundaries (LAGB) which are known to have a (100) direction of the dislocation lines [11,15]. Examples of both types are shown in figs. 3a and 3b. Both the crystallographic orientation and the fact that the same arrays of these dislocations were observed in a number of wafers along the axis of ingot suggest that they originate from the seed. Such dislocations called “E” were already shown by X-ray topography in (110) longitudinal sections of Sidoped GaAs crystals [16]. Previously we reported the presence of not typical shallow pits on all G and G-S dislocation-related etch hillocks (see fig 4H in ref. [6]). However, further detailed optical study after shallow and deep DSL photoetching performed on wafers from the same GaAs ingot did not reveal the presence of any pits. LST examination of large central part of the wafers which
Fig. 2. Dislocations and decoration microdetects in Si-doped. (ia-nch (iaAs crystal: (a) etch hillocks (H) and shallow pit (t’) alter DSL photoetching; (b) LST image of decoration microdefects.
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/ Decoration microdefects in LEC-grown Si-doped GaAs
were subsequently photoetched did not disclose any decoration particles either see fig 3c. At the same time both DSL and LST showed the presence of some decoration precipitates close to the edges of the examined wafers. Therefore we condude that al~G and G-S dislocations in the central part of the GaAs ingot grown from stoichiometric melt are free of any decoration particles. Previously recorded pits after DSL photoetching might have been caused rather by the chemistry-related factors of the Cr03—HF—H20 etching system, than —
by the presence of any structural features along the dislocation lines. Additional peculiar features, observed both after DSL and LST examination, are the overall
microroughness (M in figs. 3a and 3b) and the background scattering on the dislocation free matrix, respectively. The latter effect is well seen when the laser beam is cut off for some time, as shown in fig. 4. Similar features were already observed in Si-doped crystals from another manufacturer [17]. Both experimental facts suggest the presence in the matrix of nanometer-scale defects in very high density, uniformly distributed in the micro-scale. These might be small dislocation loops or precipitates, such as observed by HVTEM in the matrix of the dislocation cells in SI undoped GaAs crystals [18]. Additional arguments indicating the presence of numerous dislocation loops have been obtained from DSL/TEM
LAGB
Fig. 3. Dislocations in Si-doped GaAs grown from stoichiometric melt. (a), (b) Etch hiflocks after DSL photoetching. (c) LST image of the area covering fragments shown in (a) and (b). For description of abbreviations, see text.
J.L Weyher et al.
/
Decoration microdefects in LEC-grown Si-doped GaAs
I
179
formed. Therefore it can be suggested that for stoichiometric melt and using dislocation free seed it is possible to grow GaAs with essentially reduced density of grown-in dislocations. (4) It has been discovered by the LST method that in all examined samples there exist submicron matrix defects. These are most probably extrinsic dislocation loops which influence the morphology of GaAs surface after DSL photoetching (microroughness).
~
Fig. 4. Background of the matrix in the GaAs crystal No. 3 evidenced by the cutting-off of the laser beam.
References study of SI GaAs after Si ion implantation followed by rapid thermal annealing. The overall microroughness which appears after DSL photoetching of implanted material [19] is now well correlated by TEM with ioops of interstitial type [20]. The alternative possibility of the existence of small As precipitates in the matrix of our Si-doped GaAs has to be rather exluded because neither shallow pits nor denuded zones around dislocations are present (see figs. 3a and 3b) as was reported in ref. [21].
Conclusions (1) In LEC-grown GaAs doped with Si to the level of carrier concentration fl = (1—2) X 1018 cm the composition of melt is decisive for the formation of microdefects and density of grown-in dislocations in the central part of the ingots. (2) The decoration microdefects are: (1) As precipitates (in GaAs grown from As-rich melt) and (2) complex microdefects such as entangled dislocation loops and/or precipitates resistant to the DS etchant (in GaAs grown from Ga-rich melt). No decoration microdefects recognizable by the DSL photoetching and LST method are present in the material grown from stoichiometric melt. (3) The density of grown-in dislocations is evidently related to the presence and type of decorating microdefects, being the highest for As-rich growth conditions, i.e. when As precipitates are ~,
[1] D.E. Holmes, R.T. Chen, K.R. Elliott, C.G. Kirkpatrick and Ph. Won Yu. IEEE Trans. Electron Devices, ED-29 (1982) 1045. [2] T. Inada, T. Sato. K. Ishida,T. Fukuda and S. Takahashi, J. Electron. Mater. 15 (1986) 169. [3] K. Terashima, in:, Semi-Insulating Ill—V Materials, Malmo, 1988, Eds. G. Grossmann and L. Ledebo (Huger, Bristol, 1989) p. 413. [4] R. Forn~. J. Crystal Growth 94 (1989) 433. [5] R. Fornari, C. Fngeri and R. Gleichmann, J. Electron. Mater. 18 (1989) 189. [6] G. Frigerio. C. Mucchino, J.L. Weyher, L. Zanotti and C. Paorici, J. Crystal Growth 99 (1990) 685. [7] J.L. Weyher and J. van de Yen, J. Crystal Growth 63 (1983) 285. [8] T. Ogawa, in: Defect Recognition and Image Processing m Ill—V Compounds (DRIP), Ed. J.P. Fillard (Elsevier, p. J.L. 1. Weyher, M. Asgarina and P.C. [9] Amsterdam, J.P. Fillard, 1985) P. Gall, Montgomery, in: Semi-Insulating Ill—V Materials, Malmo, 1988, Eds. G. Grossmann and L. Ledebo (Hilger, Bristol, 1989) p. 537. [101A.G. Cuffis, P.D. Augustus and DJ. Stirland, J. Appi. Phys. 51(1980) 2556. [11] J.L. Weyher and J. van de Ven, J. Crystal Growth 78 (1986) 191. [12] ED. Bourret, A.G. Elliot, B.-T. Lee and J.M. Jaldevic, in: Defect Recognition and Image Processing in Ill—V Compounds II (DRIP II), Ed. E.R. Weber (Elsevier, Amsterdam, 1987) p. 95. [13] C. Frigen and J.L. Weyher, J. AppI. Phys. (1989) 4646. [14] J.L. Weyher and L.J. Giling, in: Defect Recognition and Image Processing in Ill—V Compounds (DRIP), Ed. J.P. Fillard (Elsevier, Amsterdam, 1985) p. 63. [15] Phys. Chem. (1962)G.1353. [16] D.B. A.G. Holt, Elliot,J.Chia-Li Wei, Solids R. Farraro, Woolhouse, M. Scott and R. Hiskes, J. Crystal Growth 70 (1984) 169. [17] J.L. Weyher and P. Gall, CEM-USTL Report for Wacker Chemitronic GmbH, Montpellier, March 1988.
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/ Decoration microdefects in LEC-grown Si-doped GaAs
[18] F.A. Ponce, F.-C. Wang and R. Hiskes, in: Semi-Insulating Ill-V Materials, Kah-nee-ta, Warm Springs, OR, 1984, Eds. D.C. Look and J.S. Blakemore (Shiva, Nantwich, 1984) p. 68. [19] M. Dc Potter, W. Dc Raedt, M. Van Hove, M. Van
Rossum and J.L. Weyher, in: Proc. E-MRS Meeting, 1987, Vol. XVI, Eds. Y.I. Nissim and P.A. Glasow (Les Editions de Physique, Paris, 1987) p. 227. [20] J.L. Weyher and C. Frigeri, unpublished results. [21] K. Yamada and J. Osaka, J. AppI. Phys. (1988) 2609.