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Solution growth CdGeP2 crystals and layers
Journal ofCrystal Growth 50(1980)567—570 © North-Holland Publishing Company
LETTER TO THE EDITORS
SOLUTION GROWTH CdGeP2 CRYSTALS AND LAYERS
*
I. MIOTKOWSIU and S. MIOTKOWSKA Institute of Physics, Polish Academy of Sciences, Department of Crystal Growth Physics and Electron Technology, Michalowska 1,26-600 Radom, Poland
and
A. HORAK Institute of Steering Systems “Mera ‘~ Katowice, Poland Received 28 August 1979; manuscript received in final form 1 April 1980 3 were produced. Preliminary CdGeP2 attempts crystals and have layers beenhave madebeen to obtain grownCdGeP from molten bismuth. Crystals with the size of 12 X 4 X 3 mm 2 layers on germanium substrates. It was found that deposition of CdGeP2 layers is possible, but without epitaxial growth. Some observations were made as regards the growth mechanismof the layer.
Cadmium gennanium diphosphide is one of the
processes were carried out in a closed quartz ampoule 25 cm long and about 25 mm in diameter. The source ternary material was prepared by synthesis from binary CdP2 phosphide and germanium taken in stoichiometric proportions. All materials used were of high purity; of grades of SN or better. The presynthe-
II—IV—V2 semiconductors which have been intensively investigated because of their interesting physical properties and applications [1]. CdGeP2 crystals have been obtained from the liquid phase by solidification of stoichiometric melts and from the vapour phase by chemical transport [2—4]. Monocrystailine samples of this compound have also been grown from metal solutions [5,6]. In most cases tin was used as a solvent. This solvent, however, was found unsuitable for the growth of CdGeP2 due to formation of CdGe1 ~~Sn~P2 type solid solutions. The growth of CdGeP2 crystals from solution in molten lead has been reported by Mifier et al. [7], and an account of the techniqueused has been published [8,91. Although there have been a number of reports dealing with CdGeP2 crystal growth, no data concerning preparation of layers are available. CdGe1 ~Sn~P2 layers grown from molten tin have been reported by Valovetal. [10]. This letter reports the growth of CdGeP2 crystals and layers from molten bismuth. The growth
Cd Ge P~+Bi
Cd F~ IL
*
Most of this work was done at the Department of Solid State Physics of the Polish Academy of Sciences, Kawalca 3, Zabrze, Poland.
Temperature Fig. 1. A schematic representation of the growth ampoule and temperature profile along the furnace. 567
I. Miotkowski, S. Miotkowska / Solution growth of CdGeP
568
2
vapour pressure of about 3900 Torr. This value of
b • -.-
of CdGeP2 at the temperature of about 830°C according to Borschevsky et al. [11]. An example of the CdGeP2 crystals grown in this pressure was nearly the same as the vapour pressure 3. manner is shown in fig. 2. In most cases, they grew as prisms havingplatelets Occasionally, maximum of about sizes 6ofX 412XX24mm3 X 3 mm were
-
obtained. The crystals had a metallic appearance and exhibited well-formed facets. Back reflection Laue photographs and powder X-ray diffraction showed that ternary material was produced.
-
Fig. 2. Typical CdGeP
Preliminary attempts of the growth of CdGeP2 layers were carried out using the apparatus shown in fig. 3. A solution of 90 mol% of bismuth and 10 mol% of presynthesized CdGeP2 was placed in a carbon vessel closed at a bottom by slide-bar which held a substrate. The solution was brought into contact with the substrate by the movement of slide-bar which was realized electromagnetically. In order to prepare CdGeP2 layers, the same experimental arrangements were applied as for crystal growth. After heating to 790°Cand holding at this temperature for several hours to homogenize the solution, the ampoule was cooled slowly to 730°C. At this point, the substrate was removed from under the solution and then the ampoule was rapidly cooled to room temperature. n-Type germanium slices of (111) orientation were used as substrates after mechanical and chemical treatment in CP-4 mixture.
2 crystals grown from liquid bismuth.
sized material and an appropriate quantity of solvent to obtain 15 mol% solution, were located in a quartz vessel and inserted in an ampoule, as shown schematically in fig. 1. After evacuation to i0~Torr, the tube was sealed off and placed in a two-zone furnace. it was next heated at a rate of 80°C/hup to 810— 830°C. After holding for several hours the ampoule was slowly cooled at a rate of 1—4°C/hto a temperature of about 700—720°C.At this point, the arnpoule was removed from the furnace and inverted to decant the solvent. During both heating and crystal growth periods the vapour pressure of Cd and P could be controlled by the use of some excess of binary phosphide placed at the bottom of the ampoule. The temperature of CdP2 was about 770°C, corresponding to a total
e~ektromagnet graphite vacuum isoLation
tubes
th ermocouple7/
~? ~
rtz
~J~1T ~
\\
Cd P 2
~\Ge
su
bstrate Fig. 3. The equipment being used for CdGeP2 layers growth in a sealed system.
I. Miotkowslci, S. Miotkowska / Solution growth of CdGeF
2
F
~
--
Hg. 4. Typical appearance of polycrystalline layer grown on (11 1)-oriented germanium substrate.
Fig. 4 shows the typical appearance of the layers cooled at a rate of about 4°C/h.The thickness of the layers obtained is variable along the substrate. The polycrystalline nature of these layers was determined by electron-microscope diffraction patterns, and no epitaxial growth was observed. Some preliminary experiments were also made to explain the growth mechanism of the layers. In these experiments, the growth of the material took place in turn on different sections of the substrate which allowed observation of the following stages of deposi tion. Only a part of the substrate was removed from under the solution after the first time period of the growth, so that further growth could be achieved on the remaining part of the substrate. Fig. 5 shows the appearance of the substrate surface after cooling for several hours at a rate of about 3°C/h.After the first time period a large number of small separately distributed crystallites was deposited on the substrate. During further growth the size of the crystallites was increased and part of them were joined in, as seen in fig. 5a. Fig. Sb shows the layer obtained in another run using the procedure as described above. In this case, both the first and second time periods of the growth were longer. After the first time period, the part of the substrate removed from under the solution was
569
1
P
/
_______________________________ ~
-
• 1’
-__________________
b Fig. 5. The surface of germanium substrate after two-stage growth: (a) I period 2.5 h, II period 3 h; (b) I period 6 h, II period 3 h.
covered with connected crystallites. After the second period, the growth of a continuous layer was observed on the remaining part of the substrate. However, it was observed that the whole surface of the substrates was not entirely coated with the growing layer. The authors would like to thank Mr. J. Weszka for assistance in preparing the samples. We are also much
570
I. Miotkowski, S. Miotkowska / Solution growth of CdGeP
2
indebted to Dr. Brian Paniplin for helpful comments
[411.Miotkowski, J. Weszka, J. Jurusik and S. Miotkowska,
on this paper.
J. Crystal Growth 48(1980) 479. [5] B.R. Pamplin and A.J. Springthorpe, J. Crystal Growth 3/4 (1968) 313.
R ef erences
[6] S.A. 196 Mughal, 895 AJ. Payne and B. Ray, J. Mater. Sci. 4 [7] A. Millar, G.D. Holah and W.C. Clark, J. Phys. Chem.
[1] J.L. Shay and J.H. Wernick, Ternary Chalcopyrite Semiconductors Growth Electronic Properties and Apphcations(Pergamon 1975) [2] K. Masumoto, S. Isomura and W. Goto, J. Phys. Chem. Solids 27(1966)1939. [31 E. Buehler, J.H. Wernick and J.D. Wiley, J. Electron. Mater. 2 (1973) 445.
Solids 35 (1974) 685. [8] B R Pamplin J Crystal Growth 26 (1974) 239 [9] B R Paniphn J Physique 36 C3 (1975)35 [10] Y.A. Valov, N.A. Goryunova, E.I. Leonov and V.M. Orlov,Acta Phys. Hung. 33 (1973) 1. [11] A.S. Borschevsky, Y.K. Undalov andT.M. Schantzavoy, Neorg. Mater. 13 (1977) 22.
LETTER TO THE EDITORS
SOLUTION GROWTH CdGeP2 CRYSTALS AND LAYERS
*
I. MIOTKOWSIU and S. MIOTKOWSKA Institute of Physics, Polish Academy of Sciences, Department of Crystal Growth Physics and Electron Technology, Michalowska 1,26-600 Radom, Poland
and
A. HORAK Institute of Steering Systems “Mera ‘~ Katowice, Poland Received 28 August 1979; manuscript received in final form 1 April 1980 3 were produced. Preliminary CdGeP2 attempts crystals and have layers beenhave madebeen to obtain grownCdGeP from molten bismuth. Crystals with the size of 12 X 4 X 3 mm 2 layers on germanium substrates. It was found that deposition of CdGeP2 layers is possible, but without epitaxial growth. Some observations were made as regards the growth mechanismof the layer.
Cadmium gennanium diphosphide is one of the
processes were carried out in a closed quartz ampoule 25 cm long and about 25 mm in diameter. The source ternary material was prepared by synthesis from binary CdP2 phosphide and germanium taken in stoichiometric proportions. All materials used were of high purity; of grades of SN or better. The presynthe-
II—IV—V2 semiconductors which have been intensively investigated because of their interesting physical properties and applications [1]. CdGeP2 crystals have been obtained from the liquid phase by solidification of stoichiometric melts and from the vapour phase by chemical transport [2—4]. Monocrystailine samples of this compound have also been grown from metal solutions [5,6]. In most cases tin was used as a solvent. This solvent, however, was found unsuitable for the growth of CdGeP2 due to formation of CdGe1 ~~Sn~P2 type solid solutions. The growth of CdGeP2 crystals from solution in molten lead has been reported by Mifier et al. [7], and an account of the techniqueused has been published [8,91. Although there have been a number of reports dealing with CdGeP2 crystal growth, no data concerning preparation of layers are available. CdGe1 ~Sn~P2 layers grown from molten tin have been reported by Valovetal. [10]. This letter reports the growth of CdGeP2 crystals and layers from molten bismuth. The growth
Cd Ge P~+Bi
Cd F~ IL
*
Most of this work was done at the Department of Solid State Physics of the Polish Academy of Sciences, Kawalca 3, Zabrze, Poland.
Temperature Fig. 1. A schematic representation of the growth ampoule and temperature profile along the furnace. 567
I. Miotkowski, S. Miotkowska / Solution growth of CdGeP
568
2
vapour pressure of about 3900 Torr. This value of
b • -.-
of CdGeP2 at the temperature of about 830°C according to Borschevsky et al. [11]. An example of the CdGeP2 crystals grown in this pressure was nearly the same as the vapour pressure 3. manner is shown in fig. 2. In most cases, they grew as prisms havingplatelets Occasionally, maximum of about sizes 6ofX 412XX24mm3 X 3 mm were
-
obtained. The crystals had a metallic appearance and exhibited well-formed facets. Back reflection Laue photographs and powder X-ray diffraction showed that ternary material was produced.
-
Fig. 2. Typical CdGeP
Preliminary attempts of the growth of CdGeP2 layers were carried out using the apparatus shown in fig. 3. A solution of 90 mol% of bismuth and 10 mol% of presynthesized CdGeP2 was placed in a carbon vessel closed at a bottom by slide-bar which held a substrate. The solution was brought into contact with the substrate by the movement of slide-bar which was realized electromagnetically. In order to prepare CdGeP2 layers, the same experimental arrangements were applied as for crystal growth. After heating to 790°Cand holding at this temperature for several hours to homogenize the solution, the ampoule was cooled slowly to 730°C. At this point, the substrate was removed from under the solution and then the ampoule was rapidly cooled to room temperature. n-Type germanium slices of (111) orientation were used as substrates after mechanical and chemical treatment in CP-4 mixture.
2 crystals grown from liquid bismuth.
sized material and an appropriate quantity of solvent to obtain 15 mol% solution, were located in a quartz vessel and inserted in an ampoule, as shown schematically in fig. 1. After evacuation to i0~Torr, the tube was sealed off and placed in a two-zone furnace. it was next heated at a rate of 80°C/hup to 810— 830°C. After holding for several hours the ampoule was slowly cooled at a rate of 1—4°C/hto a temperature of about 700—720°C.At this point, the arnpoule was removed from the furnace and inverted to decant the solvent. During both heating and crystal growth periods the vapour pressure of Cd and P could be controlled by the use of some excess of binary phosphide placed at the bottom of the ampoule. The temperature of CdP2 was about 770°C, corresponding to a total
e~ektromagnet graphite vacuum isoLation
tubes
th ermocouple7/
~? ~
rtz
~J~1T ~
\\
Cd P 2
~\Ge
su
bstrate Fig. 3. The equipment being used for CdGeP2 layers growth in a sealed system.
I. Miotkowslci, S. Miotkowska / Solution growth of CdGeF
2
F
~
--
Hg. 4. Typical appearance of polycrystalline layer grown on (11 1)-oriented germanium substrate.
Fig. 4 shows the typical appearance of the layers cooled at a rate of about 4°C/h.The thickness of the layers obtained is variable along the substrate. The polycrystalline nature of these layers was determined by electron-microscope diffraction patterns, and no epitaxial growth was observed. Some preliminary experiments were also made to explain the growth mechanism of the layers. In these experiments, the growth of the material took place in turn on different sections of the substrate which allowed observation of the following stages of deposi tion. Only a part of the substrate was removed from under the solution after the first time period of the growth, so that further growth could be achieved on the remaining part of the substrate. Fig. 5 shows the appearance of the substrate surface after cooling for several hours at a rate of about 3°C/h.After the first time period a large number of small separately distributed crystallites was deposited on the substrate. During further growth the size of the crystallites was increased and part of them were joined in, as seen in fig. 5a. Fig. Sb shows the layer obtained in another run using the procedure as described above. In this case, both the first and second time periods of the growth were longer. After the first time period, the part of the substrate removed from under the solution was
569
1
P
/
_______________________________ ~
-
• 1’
-__________________
b Fig. 5. The surface of germanium substrate after two-stage growth: (a) I period 2.5 h, II period 3 h; (b) I period 6 h, II period 3 h.
covered with connected crystallites. After the second period, the growth of a continuous layer was observed on the remaining part of the substrate. However, it was observed that the whole surface of the substrates was not entirely coated with the growing layer. The authors would like to thank Mr. J. Weszka for assistance in preparing the samples. We are also much
570
I. Miotkowski, S. Miotkowska / Solution growth of CdGeP
2
indebted to Dr. Brian Paniplin for helpful comments
[411.Miotkowski, J. Weszka, J. Jurusik and S. Miotkowska,
on this paper.
J. Crystal Growth 48(1980) 479. [5] B.R. Pamplin and A.J. Springthorpe, J. Crystal Growth 3/4 (1968) 313.
R ef erences
[6] S.A. 196 Mughal, 895 AJ. Payne and B. Ray, J. Mater. Sci. 4 [7] A. Millar, G.D. Holah and W.C. Clark, J. Phys. Chem.
[1] J.L. Shay and J.H. Wernick, Ternary Chalcopyrite Semiconductors Growth Electronic Properties and Apphcations(Pergamon 1975) [2] K. Masumoto, S. Isomura and W. Goto, J. Phys. Chem. Solids 27(1966)1939. [31 E. Buehler, J.H. Wernick and J.D. Wiley, J. Electron. Mater. 2 (1973) 445.
Solids 35 (1974) 685. [8] B R Pamplin J Crystal Growth 26 (1974) 239 [9] B R Paniphn J Physique 36 C3 (1975)35 [10] Y.A. Valov, N.A. Goryunova, E.I. Leonov and V.M. Orlov,Acta Phys. Hung. 33 (1973) 1. [11] A.S. Borschevsky, Y.K. Undalov andT.M. Schantzavoy, Neorg. Mater. 13 (1977) 22.