The solution crystallization method was used to obtain Ga(z)In(1-x)P alloys for all values of x desired between zero and 1. The method of preparation makes it possible to crystallize the solid at a constant temperature. The points obtained by cathodoluminescence are nearly in straight lines. The optical absorption thresholds are confirmed in the results and make it possible to define the nature of the transitions except when x is in the neighborhood of 0.65. These determinations agree with those of Hilsum and Porteus (1968), but are not in agreement with those obtained by Lorenz et al, (1968)

Bourneix, J.

Horak, J.

Rodot, H.

Rouy, G.

English

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NASA TECHNICAL MEMORANDUM NASA TM-88431
e
PREPARATION AND OPTICAL PROPERTIES OF GA^N^-^P ALLOYS
H. Rodot, J. Horak, G. Rouy and J. Bourneix
Translation of "Elaboration et proprietes optiques d'alliages
Ga^In, P", Academie des Sciences (Paris), Comptes Rendus, Serie B-
Sciences Physiques, Vol. 269, No. 9, September 1, 1969, pp. 381-384,
{N&S&-IM-88131) PBEPAESTIGN AND OPTICAL N86-30518
PBOPEEIIES OF G£{X) IN (1-X)£> flllOYS |National
Aeronautics and Space administration) 9 p
CSCL 20L Dnclas
G3/76 43515
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546 MAY 1986
https://ntrs.nasa.gov/search.jsp?R=19860021046 2020-03-20T13:28:02+00:00Z
NA-SA
7. G«««rn/««nt A««t«ton H«.
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PREPARATION AND OPTICAL PROPERTIES OF
GAXIN1-XP ALLOYS
3. R<po«i O«r«
M a y , 1986
7.
H. Rodot, J. Horak, G. Rouy and J.
Bourneix; National Center of Scientif-
ic Research, Hauts-de-Seine , Paris
O«g«A4l«fi«*
10. N..
Leo Kanner Associates
Redwood City, California 94063
II. Contract •• C<««< N«
NASw- !4005
Translation
I?, Jp^oto'.nj Ag«n<r He^« «i4 A44>««
National Aeronautics and Sp-ace Admin-
istration, Washington, D.C. 20546
IS.
translation of: "Elaboration et proprietes optiques d'alliages
-Ga In., P", IN: Academic des. Sciences (Paris), Comntes Rendns,
Serie B^ Sciences Physiques, Vol. 269, No. 9, September 1, 1969,
pp. 38T-384 (A70-10661)
Use of the solution crystallization method to obtain --•?.."
Ga In, P alloys for all values of x desired between zero and
l.z Thexmethod of preparation makes it possible to crystallize
the solid at a constant temperature. The points obtained by
cathodoluminescence are nearly in straight lines. Ttie optical
absorption thresholds are confirmed in the results" and make it
possible to define the nature of the transitions except when x
is in the neighberhood of 0.65. These determinations agree
with those of Hilsum and Porteus (1968), but are not in agree-
ment with those obtained by Lorenz et al. (1968).
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PREPARATION AND OPTICAL PROPERTIES OF GA^N^^ ALLOYS
H. Rodot, J. Horak, G. Rouy and J; Bourneix
National Center of Scientific Research, Laboratory of Magnetism and
Physics and Solids, Bellevue, Hauts-de-Seine, France
It has been recently demonstrated that the semiconductor
Ga In, P alloys existed for all the values of x. Different optical
2 J. ~~ X
measurements have been accomplished on these materials in order to
know the energy and the character (direct or indirect) of the transi-
tions between bands of valence and of conduction. However, the re-
sults obtained [1, 2] are not in agreement, which may be due, in par-
ticular, to the difficulty of obtaining, by the standard methods for
elaboration, of homogeneous crystals.
The utilization of the solution crystallization method, already
experimented with for gallium phosphate [3], has allowed these alloys
to be obtained for all the values of x desired between 0 and 1. On
the crystals obtained, the value of x has been measured by electronic
microanalysis, while also estimating by cathodpluminescence the wave-
length of the light emitted by the sample. In order to locate with
more precision the boundary zone between the direct transition and
indirect transition alloys, measurements of optical absorption have
been carried out.
The method of elaboration in solution that has been utilized al-
lows crystallization of the solid at a constant temperature, depend-
ing on the concentration of the liquid in phosphorous at the inter-
face of crystallization. This is a favorable factor when the compo-
sition of the alloy depends very strongly on the temperature of crys-
tallization, as in the present case. An indium-gallium mixture is
Numbers in the margin indicate pagination of the foreign text.
utilized as a base, in which the phosphorous is made to diffuse ac-
cording to the process described in [3]. For a given concentration
of the liquid solution in gallium, the free energy of the liquid
phase at the solid-liquid interface depends on the temperature; the
free energy of the solid being equal to that of the liquid, the com-
position of the solid depends on that of the liquid.
The composition of the alloy obtained has been determined exper-
imentally, as a function of the concentration in gallium of the base,
for a temperature of crystallization 1^=850.to 950°C. Figure 1 il-
. L*
lustrates the case of TC = 900°C. When TC<850°'C, the speeds of diffu-
sion of the different molecules at the interface of crystallization
becoming very low, the segregation of the base is incomplete and in-
clusions are observed in the alloy if the speed of crystallization is
too great. For this speed to be low, the solution must be fed under
-4
a very reduced pressure of phosphorous (-2'10 atm) and the tempera-
ture of the surface of the base must be very low, approximately
1050°C, in order to decrease the solubility of the phosphorous in the /382
In-Ga mixture. The temperature of the coolest point of the cell is
adjusted as a function of the temperature gradient of the liquid col-
umn, so that the speed of crystallization is on the order of 0.10
mm/h and even possibly lower (c.f. [3]).
Ql
I
OB
Q6
CM
02|.
Temperature de cristallisafion 900*C
In 3 Si 7 3 ZO 40 60 80 Go
Goncentratibn en% mo), de 60
Figure 1.
Key: 1-Temperature of crystallization 900°C 2-Concentration in
mol. of Ga.
The InP compound presents, at 300°K, a grounded band E from
O
1.27 eV with direct transition and toward 2.1 eV an indirect transi-
tion. At 300°K, there are found in GaP direct transitions at 2.75 eV
and indirect transitions at 2.25 eV. In the systems of alloys, E
o
frequently varies linearly with the composition which, for Ga In, P
Z -L ™°~ X
leads to straight lines (1) and (2) (figure 2) respectively for the
direct and indirect transitions.
xltf
is
10
X=05+ I
X=0.43
1.8 1.9 2.0
Figure 2.
In order to determine experimentally the width of the grounded
band of the alloys as a function of their concentration x in gallium,
the Castaing probe has been utilized, on the one hand by electronic
microanalysis and, on the other hand, for a visual determination of
the cathodoluminescence. This gives the possibility of estimating
the width of the optical grounded band exactly at the site of the
measurement of concentration. The micro-probe (Canseca, MS 46) was
utilized with an excitation voltage of 15 kV and a probe current of
30 to 100 nA. The gallium content was determined by means of the Ka,
radiation with a quartz spectrometer 11YO or 10T1 ; for indium, the
La, radiation was utilized and a quartz spectrometer 10TO. The sam-
ple was made from GaP and InP compounds.
For the visual estimation of the luminescence under electron
beams, operations have proceeded in the following manner. It is
found that, for 0.3<x<0.7, the luminescence of the alloys possesses
easily identifiable zones of wavelength, which are the red-orange /383
transition at 2.00 eV, orange-yellow at 2.06 eV and yellow-green at
2.18 eV. The concentration of the samples emitting in these zones is
reported on figure 2, as well as the mean values of concentrations
obtained on thematerials emitting the yellow and in the orange. It
is observed that the change of slope appears to be situated at the
transition from yellow to green and for a value of x=0.63 to 0.65.
In order to refine these results, the optical absorption of sam-
ples of different thicknesses (d=15 to 500 y) has been measured. In
order to attain a great power of resolution, the slit of the spec-
_2
trometer was very narrow (3 to 5-10 mm). The absorption coeffi-
cient K has been calculated according to the formula:
The values of the reflexion coefficient R have been determined
for the pure GaP and InP compounds. In order to calculate the value
of K for the Ga In, P alloys, there has been taken R=0.27 for 0.6<x
^ -L """ X.
<1, R=0.28 for 0<x<0.6. The low variations of the value of R in the
range of the wavelengths situated below the threshold of absorption
of the alloys influence little the value of K.
For 0.62<x<l, figure 3 demonstrates that the relationship K~
2(hw-E ) is respected, the transitions allowed are thus indirect.
O
For the concentrations 0<x<0.60, there have been found, in the
range of high absorptions, direct transitions (figure 4).
24 Q Q7 CK Q6 0.6 X
The values of E measured by absorption are presented on figure
O
2 (triangles). It is observed that, for x near 0.65, these values
are lower than those obtained with cathodoluminescence. This appears
to be connected to the fact that there is found a zone of transition
where it is difficult to interpret the curves of optical absorption.
Conclusions
First of all, it is possible to observe that the points obtained
by cathodoluminescence are close to straight lines (1) and (2). The
thresholds of optical absorption confirm the assemblage of these re-
sults and allow precise definition of the nature of the transitions,
except for x close to 0.65. These determinations are in agreement
with the results obtained by [1], which are shown on figure 2 . •
(crosses) and are also situated close to straight lines (1) and (2).
On the contrary, the results obtained by [2], represented on figure 2
(dotted curve), do not agree with the authors', particularly for the
alloys with direct transitions. The method for determination and the
quality of the alloys are perhaps responsible for such a difference
in the results. The authors' method for elaboration in solution is
demonstrated to be particularly effective in the case of these al-
loys .
REFERENCES
1. Hilsum, C. and P. Porteus, Proc. IX Int. Conf. Phys. Semicond.,
Moscow, .pp. 1214-1216, 1968.
2. Lorenz, M.R. et al. , Appl. Phys. Lett. 13. 421-423 (1968).
3. Rodot, H. et al., Proc. II Int. Conf. Crystal Growth, J. Cryst.
Growth 3/4. 305-308 (1968).


Preparation and optical properties of GA(x)IN(1-x)P alloys

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