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Low-defect InSb crystal growth by InN doping
Journal of Crystal Growth 47 (1979) 746—748 © North-holland Publishing Company
LETTER TO THE EDITORS LOW-DEFECT lnSb CRYSTAL GROWTH BY InN DOPING Kazutaka TERASHIMA Research and Development Center, Toshiba Corporation, 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Japan Received 24 November 1978; manuscript received in final form 24 July 1979
Low detect lnSb single crystals were found to be grown by doping with InN, using the Czochralski technique. The InN doped lnSb crystals were investigated by etching study, and compared with undoped crystals. A drastic decrease was revealed in punching3. High quality photoout defects (P-pits) and saucer-like-pit defects (S-pits), caused by doping with more than 1.5 X 1017 cm conductive infrared detectors were prepared by u sing the crystal.
InSb is one of the most attractive materials for applications such as an infrared detector and a Hall sensor, because of its direct, small energy gap and large carrier mobility, and ease of preparation of single crystal due to the relatively low temperature. Hitherto, many physical and practical properties in device applications of the crystal have been investigated [1,21. The use of InSb in infrared detector devices requires the establishment of growth conditions for high quality crystals having few defects affecting noise and inhomogeneity of sensitivity. Many papers have been published on the growth of InSb [3,4], but there is no report available on the growth of high quality crystals for infrared detector devices. Low defect InSb single crystals were found to be grown by doping with InN, using the Czochralski technique, and to be of high quality for infrared detector devices. This paper is concerned with the growth and characterization of InN-doped lnSb crystals. InSb single crystals were grown by the Czochralski technique, along the (211> direction, in an atmosphere of high purity forming gas (7N grade nitrogen includ ing 10—20% 7N grade hydrogen). As the source materials, high purity polycrystalline ingot was used, which was refined many times in an atmosphere of high purity (7N grade) hydrogen by the zone refining process. Before a polycrystal InSb ingot was charged into a quartz crucible, InN (99.999% CERAC Co.)
was added onto the bottom of the crucible, and a particle of highly Ge-doped InSb was added to grow a p-type InSb single crystal whose carrier concentration was less than I X 1014 cm3 at 77 K. As an example of the amount of charge, about 170 g polycrystalline ingot, highly 0.7 g Ge-doped InSb and 1 mg InN was used. The starting material was heated to about 600°C and melted. After melting, the crucible was kept for about one hour at 560°C to dissolve InN homogeneously into molten InSb. (ill) wafers cut from the middle of the crystal boule were used for etching study. The ~safers were
__________________________________________________
-_______________
I ie. I . A t’~pic~lInS h single en st~len os n in di pin’ v~Oh Irl~’~.it 1.5 x 1017 c1n3 concentration in molten lnSb, pulled along the(211) direction. 746
K. Terashima /Low-defect InSb crystal growth by InN doping
0
747
3
-
*
~
59gm
!OO~u.m
“
-
Fig. 3. A typical l’-pit is shown. The P-pit center is denoted by C. Many pair pits follow a line extending in 1110] direc-
tion.
I
D
P
-
~ I~j~jJjjj~U~t ~‘ ~JI1I~WI
was observed at a concentration below 1.2 X 1018 nitrogen atoms ci113 which was the upper limit of this study. The InN doped lnSb showed a tendency
to thinner the [111] direction, compared withbecome undoped InSb in crystals. An etched surface of InN-doped InSb is shown in
~
S p
1 ig. 2. Ia) l.tclied (11 1)ln surface for InN-doped InSb at concentration of 1.5 x i01 ~ nitrogen atoms cm3 in molten lnSb. (b) Etched (11 l)In surface for InN-doped InSb.
fig. 2, as compared with that of an undoped InSb. In the undoped InSb crystals, many etch pits are revealed, as shown in fig. 2b. These pits can be clas-
sified into D-pits (dislocation defects), S-pits (saucerlike-pit defects), and P-pits (punching-out defects), denoted by D, S, and P, respectively, in fIg. 2b. A
S PIT
0
etched at room temperature by using 1 part 49% HF 2 parts 30% H 202 : 2 parts H20 as an etchant for detecting etch pits. The lattice constant of the crystal (ao) was measured at 25°Cby the Bond method using CuKa1 radiation. Well formed InN-doped InSb single crystals, ranging in size from 15 to 25 mm in diameter and from 60 to 70 mm in length could be grown with 15—18 -
.
.
mm/h and 23 rpm pulling and rotation rates, respectively. A typical InN-doped InSb single crystal is shown in fig. 1. The crystal grown from theatoms melt at a concentration of 1.5was X 1017 nitrogen cn~3. No macroscopic precipitation of InN in InSb
~ o~
~ prr I
..~
olO
2
._
a-
~——1——A———. ~~ ~ I \~ ‘~—.L
10’ 0
6
7
10 0 0 0 3} Nitrogen Concentration in Melt (cm Fig. 4. S and P etch pits densities, as a function of nitrogen atoms concentration in molten InSb.
K. Terashirna /Low-dc feet InSb crystal growth by InN doping
748
s-—---i c~
decibels and the inliomogeneity of the sensitivity was --~
—
I ig. 5. Etched surface of plasticalb det’ornmed InN-doped InSb. Many D-pits follow lines e\tendjng in (1101 direction,
decreased, especially in preparing small line array devices. Pc type devices, having a D* of 5 X 1Q10 cm 2 W’ in 4 X 10—2 cm2, could be obtained from Hz’’ these crystals with high yield and good reproducibility. The impurity effects in Ill—V compound crystals have been reported by several authors [5—7]. It should be noted that the InN doping effect on InSb shows a decrease in punching-out defects (P-pits) and saucer-like-pit defects (S-pits), whereas the impurity effects reported relate to the dislocation pinning effects. The InN doping effects have not been solved
completely, at present. The interpretation by lattice factor model is in progress, based on several experimental results, which will be published in a subsequent paper.
typical P-pit in undoped crystals is shown in fig. 3. Many pair pits from the center of the P-pit follow a line extending in the [110] direction. By successive etching experiments, P-pits and S-pits were found to be localized in undoped crystals. Figs. 2a and 2b show that the P-pit and S-pit densities are decreased by doping with InN. The relation between S-pit and P-pit densities and the nitrogen atom concentration is shown in fig. 4. As shown in fig. 4, the P-pit density (‘--‘7 X 101 cn12) drastically decreases and becomes zero when the nitrogen atom concentration exceeds a value of about 1.5 X 1017 cmii3. The S-pit density (‘--‘7 X 102 cm2) also decreases at the same nitrogen atom concentration. The D-pit density was the lowest (“-‘5 X 101 cm2). D-pits were observed when wafers were plastically deformed at above 400°C and followed lines extending in the [1101 direction, as shown in fig. 5, which indicates that the D-pits are associated with dislocations. The D-pit density was not changed by doping with InN. The segregation coefficient of nitrogen atoms in InSb was not known. 1-lowever, all parts of the InN-doped InSb sh owed the same InN effect. By using an InN-doped InSb crystal, the detector noise could be decreased by several
The author wishes to thank Mr. W. Miyao and Mr. H. Nagasaka for valuable suggestions and discussions during this work. He thanks Mr. S. Inoue for his constant encouragement concerning zone-refining procedures. He also wishes to thank Dr. T. Fukuda for critical reading of the manuscript and helpful discussions.
References [1] W.W. Anderson, Infrared Phys. 17 (1977) 147. 121 iC. Kim, IEEE Trans. Electron Devices ED-25 (1978)
232. 131 H.C. Gatos, Solid State Science and Technology Award 122 (1975) 287C. (41 K.I”. Hulme and JEt. Mullin, Solid State Electron. 5 (1962)211. (5] PA. Kirkby, IEEE J. Quantum Electron. QF-l 1(1975) 562. 161 W. Swaminathan and S.M. Copley, J. AppI. Phys. 47 (1976) 4405. 171 Y. Seki, J. Matsui and H. Watanabe, J. Appl. Phys. 47 (1976) 3374. [8] Unpublished work. 191 T.I. Ol’khovikova and IL. Shul’pina, Soviet Phys.-Sohid State 10 (1969) 1678.
LETTER TO THE EDITORS LOW-DEFECT lnSb CRYSTAL GROWTH BY InN DOPING Kazutaka TERASHIMA Research and Development Center, Toshiba Corporation, 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Japan Received 24 November 1978; manuscript received in final form 24 July 1979
Low detect lnSb single crystals were found to be grown by doping with InN, using the Czochralski technique. The InN doped lnSb crystals were investigated by etching study, and compared with undoped crystals. A drastic decrease was revealed in punching3. High quality photoout defects (P-pits) and saucer-like-pit defects (S-pits), caused by doping with more than 1.5 X 1017 cm conductive infrared detectors were prepared by u sing the crystal.
InSb is one of the most attractive materials for applications such as an infrared detector and a Hall sensor, because of its direct, small energy gap and large carrier mobility, and ease of preparation of single crystal due to the relatively low temperature. Hitherto, many physical and practical properties in device applications of the crystal have been investigated [1,21. The use of InSb in infrared detector devices requires the establishment of growth conditions for high quality crystals having few defects affecting noise and inhomogeneity of sensitivity. Many papers have been published on the growth of InSb [3,4], but there is no report available on the growth of high quality crystals for infrared detector devices. Low defect InSb single crystals were found to be grown by doping with InN, using the Czochralski technique, and to be of high quality for infrared detector devices. This paper is concerned with the growth and characterization of InN-doped lnSb crystals. InSb single crystals were grown by the Czochralski technique, along the (211> direction, in an atmosphere of high purity forming gas (7N grade nitrogen includ ing 10—20% 7N grade hydrogen). As the source materials, high purity polycrystalline ingot was used, which was refined many times in an atmosphere of high purity (7N grade) hydrogen by the zone refining process. Before a polycrystal InSb ingot was charged into a quartz crucible, InN (99.999% CERAC Co.)
was added onto the bottom of the crucible, and a particle of highly Ge-doped InSb was added to grow a p-type InSb single crystal whose carrier concentration was less than I X 1014 cm3 at 77 K. As an example of the amount of charge, about 170 g polycrystalline ingot, highly 0.7 g Ge-doped InSb and 1 mg InN was used. The starting material was heated to about 600°C and melted. After melting, the crucible was kept for about one hour at 560°C to dissolve InN homogeneously into molten InSb. (ill) wafers cut from the middle of the crystal boule were used for etching study. The ~safers were
__________________________________________________
-_______________
I ie. I . A t’~pic~lInS h single en st~len os n in di pin’ v~Oh Irl~’~.it 1.5 x 1017 c1n3 concentration in molten lnSb, pulled along the(211) direction. 746
K. Terashima /Low-defect InSb crystal growth by InN doping
0
747
3
-
*
~
59gm
!OO~u.m
“
-
Fig. 3. A typical l’-pit is shown. The P-pit center is denoted by C. Many pair pits follow a line extending in 1110] direc-
tion.
I
D
P
-
~ I~j~jJjjj~U~t ~‘ ~JI1I~WI
was observed at a concentration below 1.2 X 1018 nitrogen atoms ci113 which was the upper limit of this study. The InN doped lnSb showed a tendency
to thinner the [111] direction, compared withbecome undoped InSb in crystals. An etched surface of InN-doped InSb is shown in
~
S p
1 ig. 2. Ia) l.tclied (11 1)ln surface for InN-doped InSb at concentration of 1.5 x i01 ~ nitrogen atoms cm3 in molten lnSb. (b) Etched (11 l)In surface for InN-doped InSb.
fig. 2, as compared with that of an undoped InSb. In the undoped InSb crystals, many etch pits are revealed, as shown in fig. 2b. These pits can be clas-
sified into D-pits (dislocation defects), S-pits (saucerlike-pit defects), and P-pits (punching-out defects), denoted by D, S, and P, respectively, in fIg. 2b. A
S PIT
0
etched at room temperature by using 1 part 49% HF 2 parts 30% H 202 : 2 parts H20 as an etchant for detecting etch pits. The lattice constant of the crystal (ao) was measured at 25°Cby the Bond method using CuKa1 radiation. Well formed InN-doped InSb single crystals, ranging in size from 15 to 25 mm in diameter and from 60 to 70 mm in length could be grown with 15—18 -
.
.
mm/h and 23 rpm pulling and rotation rates, respectively. A typical InN-doped InSb single crystal is shown in fig. 1. The crystal grown from theatoms melt at a concentration of 1.5was X 1017 nitrogen cn~3. No macroscopic precipitation of InN in InSb
~ o~
~ prr I
..~
olO
2
._
a-
~——1——A———. ~~ ~ I \~ ‘~—.L
10’ 0
6
7
10 0 0 0 3} Nitrogen Concentration in Melt (cm Fig. 4. S and P etch pits densities, as a function of nitrogen atoms concentration in molten InSb.
K. Terashirna /Low-dc feet InSb crystal growth by InN doping
748
s-—---i c~
decibels and the inliomogeneity of the sensitivity was --~
—
I ig. 5. Etched surface of plasticalb det’ornmed InN-doped InSb. Many D-pits follow lines e\tendjng in (1101 direction,
decreased, especially in preparing small line array devices. Pc type devices, having a D* of 5 X 1Q10 cm 2 W’ in 4 X 10—2 cm2, could be obtained from Hz’’ these crystals with high yield and good reproducibility. The impurity effects in Ill—V compound crystals have been reported by several authors [5—7]. It should be noted that the InN doping effect on InSb shows a decrease in punching-out defects (P-pits) and saucer-like-pit defects (S-pits), whereas the impurity effects reported relate to the dislocation pinning effects. The InN doping effects have not been solved
completely, at present. The interpretation by lattice factor model is in progress, based on several experimental results, which will be published in a subsequent paper.
typical P-pit in undoped crystals is shown in fig. 3. Many pair pits from the center of the P-pit follow a line extending in the [110] direction. By successive etching experiments, P-pits and S-pits were found to be localized in undoped crystals. Figs. 2a and 2b show that the P-pit and S-pit densities are decreased by doping with InN. The relation between S-pit and P-pit densities and the nitrogen atom concentration is shown in fig. 4. As shown in fig. 4, the P-pit density (‘--‘7 X 101 cn12) drastically decreases and becomes zero when the nitrogen atom concentration exceeds a value of about 1.5 X 1017 cmii3. The S-pit density (‘--‘7 X 102 cm2) also decreases at the same nitrogen atom concentration. The D-pit density was the lowest (“-‘5 X 101 cm2). D-pits were observed when wafers were plastically deformed at above 400°C and followed lines extending in the [1101 direction, as shown in fig. 5, which indicates that the D-pits are associated with dislocations. The D-pit density was not changed by doping with InN. The segregation coefficient of nitrogen atoms in InSb was not known. 1-lowever, all parts of the InN-doped InSb sh owed the same InN effect. By using an InN-doped InSb crystal, the detector noise could be decreased by several
The author wishes to thank Mr. W. Miyao and Mr. H. Nagasaka for valuable suggestions and discussions during this work. He thanks Mr. S. Inoue for his constant encouragement concerning zone-refining procedures. He also wishes to thank Dr. T. Fukuda for critical reading of the manuscript and helpful discussions.
References [1] W.W. Anderson, Infrared Phys. 17 (1977) 147. 121 iC. Kim, IEEE Trans. Electron Devices ED-25 (1978)
232. 131 H.C. Gatos, Solid State Science and Technology Award 122 (1975) 287C. (41 K.I”. Hulme and JEt. Mullin, Solid State Electron. 5 (1962)211. (5] PA. Kirkby, IEEE J. Quantum Electron. QF-l 1(1975) 562. 161 W. Swaminathan and S.M. Copley, J. AppI. Phys. 47 (1976) 4405. 171 Y. Seki, J. Matsui and H. Watanabe, J. Appl. Phys. 47 (1976) 3374. [8] Unpublished work. 191 T.I. Ol’khovikova and IL. Shul’pina, Soviet Phys.-Sohid State 10 (1969) 1678.