ASTM F418-77(1996)e1
(Practice)Standard Practice for Preparation of Samples of the Constant Composition Region of Epitaxial Gallium Arsenide Phosphide for Hall Effect Measurements
Standard Practice for Preparation of Samples of the Constant Composition Region of Epitaxial Gallium Arsenide Phosphide for Hall Effect Measurements
SCOPE
1.1 This practice covers a procedure to be followed to free the constant composition region of epitaxially grown gallium arsenide phosphide, GaAs(1x)Px, from the substrate and graded region on which it was grown in order to measure the electrical properties of only the constant composition region, which is typically 30 to 100 m thick. It also sets forth two alternative procedures to be followed to make electrical contact to the specimen.
1.2 It is intended that this practice be used in conjunction with Test Methods F 76.
1.3 The specific parameters set forth in this recommended practice are appropriate for GaAs0. 62P0. 38, but they can be applied, with changes in etch times, to material with other compositions.
1.4 This practice does not deal with making or interpreting the Hall measurement on a specimen prepared as described herein, other than to point out the existence and possible effects due to the distribution of the free carriers among the two conduction band minima.
1.5 This practice can also be followed in the preparation of specimens of the constant composition region for light absorption measurements or for mass or emission spectrometric analysis.
1.6 This practice becomes increasingly difficult to apply as specimens become thinner.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For hazard statement, see Section 9 and 11.9.2.4.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: F 418 – 77 (Reapproved 1996)
Standard Practice for
Preparation of Samples of the Constant Composition
Region of Epitaxial Gallium Arsenide Phosphide for Hall
Effect Measurements
This standard is issued under the fixed designation F 418; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made throughout in February 1997.
1. Scope 2. Referenced Documents
1.1 This practice covers a procedure to be followed to free 2.1 ASTM Standards:
the constant composition region of epitaxially grown gallium D 1125 Test Methods for Electrical Conductivity and Re-
arsenide phosphide, GaAs P , from the substrate and sistivity of Water
(1−x) x
graded region on which it was grown in order to measure the F 76 Test Methods for Measuring Resistivity and Hall
electrical properties of only the constant composition region, Coefficient and Determining Hall Mobility in Single-
which is typically 30 to 100 μm thick. It also sets forth two Crystal Semiconductors
alternative procedures to be followed to make electrical contact F 358 Test Method for Wavelength of Peak Photolumines-
to the specimen. cence and the Corresponding Composition of Gallium
1.2 It is intended that this practice be used in conjunction Arsenide Phosphide Wafers
with Test Methods F 76.
3. Terminology
1.3 The specific parameters set forth in this recommended
3.1 Definitions:
practice are appropriate for GaAs P , but they can be
0.62 0.38
applied, with changes in etch times, to material with other 3.1.1 constant composition region—as applied to epitaxial
GaAs P , the layer last grown in which the composition is
compositions.
(1−x) x
1.4 This practice does not deal with making or interpreting held fixed at about the desired value of x in mole percent
phosphorus; x is typically 0.38.
the Hall measurement on a specimen prepared as described
herein, other than to point out the existence and possible effects 3.1.2 graded region—as applied to epitaxial GaAs P ,
(1−x) x
the layer first grown in which the composition is changed from
due to the distribution of the free carriers among the two
conduction band minima. GaAs to GaAs P during the growth of the layer. The
(1−x) x
purpose of this layer is to minimize the lattice mismatch
1.5 This practice can also be followed in the preparation of
specimens of the constant composition region for light absorp- between the GaAs substrate and the GaAs P layers.
(1−x) x
−3
3.1.3 Hall carrier density—1/R e [cm ]—the reciprocal of
tion measurements or for mass or emission spectrometric
H
the product of the Hall coefficient and the electronic charge, a
analysis.
1.6 This practice becomes increasingly difficult to apply as quantity related to the charge carrier density.
specimens become thinner.
4. Summary of Practice
1.7 This standard does not purport to address all of the
4.1 In this practice (1), a specimen is cleaved from a full
safety concerns, if any, associated with its use. It is the
wafer of GaAs P , the substrate is partially removed by
responsibility of the user of this standard to establish appro-
(1−x) x
mechanical lapping, the remainder of the substrate and the
priate safety and health practices and determine the applica-
graded region are removed by chemical lapping, and the
bility of regulatory limitations prior to use. For hazard state-
specimen is contacted either by welding or by flip chip
ment, see Section 9 and 11.9.2.4.
mounting.
1 2
This practice is under the jurisdiction of ASTM Committee F-1 on Electron- Annual Book of ASTM Standards, Vol 11.01.
icsand is the direct responsibility of Subcommittee F01.15 on Gallium Arsenide. Annual Book of ASTM Standards, Vol 10.05.
Current edition approved May 27, 1977. Published July 1977. Originally The boldface numbers in parentheses refer to the list of references appended to
published as F 418-75 T. Last previous edition F 418-75 T. this practice.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 418
4.2 Complete removal of substrate and graded region is cient, since the Hall coefficient is the product of the measured
assured either by timed etching in an etchant with a composi- Hall voltage and the thickness.
tionally dependent etch rate or by measurement of composition
6.3 Nonuniform thickness can also lead to erroneous mea-
of the etched surface in accordance with Test Method F 358.
surements (see 6.2).
4.3 The thickness of the final specimen is measured micro-
6.4 GaAs P can be highly photoconductive; hence Hall
(1−x) x
scopically on a small section cleaved out of the rest of the
measurements on this material must be made in the dark.
thinned specimen.
7. Apparatus
5. Significance and Use
5.1 The efficiency of light-emitting diodes is known to vary
7.1 Hot Stage capable of heating the lapping fixture or a
with the carrier density of the starting material. This procedure
glass microscope slide to a temperature approximately 10°C
provides a technique to prepare specimens in which the Hall
above the melting point of the mounting wax (8.6).
carrier density can be measured in a region typical of that in
7.2 Lapping Fixture capable of limiting the removal by
which devices are fabricated. This quantity, which is related to
lapping of material to a final thickness of 5 6 1 mil (0.13 6
the carrier density, can be used directly as a quality control
0.03 mm).
parameter.
7.3 Glass Plate for lapping. A sheet of plate glass ⁄4by8by
5.2 Mobility is a function of a number of parameters of a
10 in. (or 7 by 200 by 250 mm) is convenient, but the exact size
semiconductor, including ionized impurity density, compensa-
is not critical.
tion, and lattice defects, some or all of which may be relatable
to material quality as reflected in device quality. Use of this 7.4 Chemical Laboratory Apparatus such as beakers,
procedure makes the measurement of the mobility of the
graduates, and tweezers suitable for handling the reagents and
constant composition region possible.
solvents used in the etching and mounting steps.
5.3 Since in GaAs P with x near 0.38, as is most often
(1−x) x
7.5 Microscope with cross hair and calibrated eyepiece
used for light-emitting diodes, the direct (000 or G) minimum
capable of measuring the specimen thickness (typically 30 to
and the indirect (100 or X) minima are within a few millielec-
100 μm) to 61% or 60.5 μm, whichever is greater.
tronvolts in energy of each other, both are populated with
7.5.1 Microscope Lamp or other source of intense white
current-carrying electrons. The mobility in the two bands is
light to illuminate the specimen by transmitted light.
significantly different, and the relative population of the two is
7.5.2 Microscope Slides and Microscope Cover Slides.
dependent upon the precise composition (x value), doping
level, and temperature. Therefore, both Hall coefficient and
7.5.3 Diamond Scribe and Metal Straight-edge or other
Hall mobility must be interpreted with care (2,3). In particular,
apparatus for cutting microscope cover slides.
a measurement of Hall carrier density will not agree with a
7.6 Specimen Mounts, each comprising an insulating ce-
carrier density measurement on the same specimen made by
ramic substrate composed of 96 % alumina with four solder-
capacitance-voltage techniques. Nevertheless, if the intent of
able regions composed of fired silver palladium paste or other
measuring the carrier density of purchased or grown specimens
solderable material (see Fig. 1).
is to find those which are optimum for diode fabrication, Hall
7.7 Contacting Apparatus as described in 7.7.1 or 7.7.2.
measurements can be of value because a curve of efficiency
7.7.1 For Flip Chip Mounting:
versus Hall carrier density can be derived for the device
process to be used based upon data taken on specimens
7.7.1.1 Strip Heater Apparatus capable of heating the
prepared in accordance with this procedure.
specimen to 425 6 25°C for a controlled time interval of a few
seconds, and then to approximately 200°C for a controlled time
6. Interferences
interval of up to 1 min, in a forming gas atmosphere.
6.1 Incomplete removal of the graded region can lead to
7.7.1.2 Low-Power Microscope suitably positioned over
spurious results, since the Hall coefficient and Hall mobility of
the strip heater to observe the specimen during the heating
the graded layer will add to those of the constant composition
cycle.
region in the usual multilayer fashion (4).
7.7.2 For Welding:
6.2 Erroneous measurement of the specimen thickness will
7.7.2.1 Fixture capable of supporting the specimen when
lead directly to an erroneous determination of the Hall coeffi-
waxed onto a glass slide while making pressure contact to the
specimen at four points on its perimeter (see Fig. 2).
7.7.2.2 Electrical Apparatus capable of charging a 0.5-μF
capacitor to 100 to 200 V and of discharging that capacitor
through an arbitrary pair of the four contacts to the specimen
(see Fig. 3).
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be
NOTE 1—All dimensions are approximate.
FIG. 1 Specimen Mount. used in all tests. All reagents shall conform to the requirements
F 418
some time after removal from the hot stage. Appropriate
caution should therefore be exercised.
9.3 Since the voltage levels available from the capacitive
discharge circuit can be high enough to cause personal injury,
the normal safety precautions required when working with
electrical apparatus should be followed.
10. Sampling
10.1 Since this procedure is destructive in nature, a sam-
pling procedure must be used to evaluate the characteristics of
a wafer or of a group of wafers. Because the most suitable
sampling plan will vary considerably depending upon indi-
vidual conditions, no general sampling procedure is included
as a part of this test procedure. For re
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.