IEC 63068-3:2020

IEC 63068-3 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Non-destructive recognition criteria of defects in
silicon carbide homoepitaxial wafer for power devices –
Part 3: Test method for defects using photoluminescence

Dispositifs à semiconducteurs – Critères de reconnaissance non destructifs des
défauts au sein d’une plaquette homoépitaxiale de carbure de silicium pour des
dispositifs d’alimentation –
Partie 3: Méthode d’essai pour les défauts à l’aide de la photoluminescence

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IEC 63068-3 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Non-destructive recognition criteria of defects in

silicon carbide homoepitaxial wafer for power devices –

Part 3: Test method for defects using photoluminescence

Dispositifs à semiconducteurs – Critères de reconnaissance non destructifs des

défauts au sein d’une plaquette homoépitaxiale de carbure de silicium pour des

dispositifs d’alimentation –
Partie 3: Méthode d’essai pour les défauts à l’aide de la photoluminescence

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.99 ISBN 978-2-8322-8614-2

– 2 – IEC 63068-3:2020 © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Photoluminescence method . 11
4.1 General . 11
4.2 Principle . 11
4.3 Requirements . 11
4.3.1 Measuring equipment . 11
4.3.2 Wafer positioning and focusing . 13
4.3.3 Image capturing . 13
4.3.4 Image processing . 13
4.3.5 Image analysis . 13
4.3.6 Image evaluation . 14
4.3.7 Documentation . 14
4.4 Parameter settings . 14
4.4.1 General . 14
4.4.2 Parameter setting process . 14
4.5 Procedure . 14
4.6 Evaluation . 14
4.6.1 General . 14
4.6.2 Mean width of planar and volume defects . 14
4.6.3 Evaluation process . 15
4.7 Precision . 15
4.8 Test report . 15
4.8.1 Mandatory elements . 15
4.8.2 Optional elements . 15
Annex A (informative)  Photoluminescence images of defects . 16
A.1 General . 16
A.2 BPD . 16
A.3 Stacking fault . 17
A.4 Propagated stacking fault . 18
A.5 Stacking fault complex . 19
A.6 Polytype inclusion . 19
Annex B (informative)  Photoluminescence spectra of defects . 21
B.1 General . 21
B.2 BPD . 21
B.3 Stacking fault . 21
B.4 Propagated stacking fault . 23
B.5 Stacking fault complex . 23
B.6 Polytype inclusion . 24
Bibliography . 25

Figure 1 – Schematic diagram of PL imaging system . 12

Figure A.1 – BPD . 17
Figure A.2 – Stacking fault . 18
Figure A.3 – Propagated stacking fault . 18
Figure A.4 – Stacking fault complex . 19
Figure A.5 – Polytype inclusion . 20
Figure B.1 – PL spectrum from BPD . 21
Figure B.2 – PL spectra from Frank-type stacking faults . 22
Figure B.3 – PL spectra from Shockley-type stacking faults . 22
Figure B.4 – PL spectra from various stacking faults in the wavelength range longer
than 650 nm . 23
Figure B.5 – PL spectrum from stacking fault complex . 24
Figure B.6 – PL spectrum from polytype inclusion . 24

– 4 – IEC 63068-3:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
NON-DESTRUCTIVE RECOGNITION CRITERIA OF DEFECTS
IN SILICON CARBIDE HOMOEPITAXIAL WAFER FOR POWER DEVICES –

Part 3: Test method for defects using photoluminescence

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 63068-3 has been prepared by IEC technical committee 47:
Semiconductor devices.
The text of this International Standard is based on the following documents:
FDIS Report on voting
47/2628/FDIS 47/2638/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 63068 series, published under the general title Semiconductor
devices – Non-destructive recognition criteria of defects in silicon carbide homoepitaxial wafer
for power devices, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 63068-3:2020 © IEC 2020
INTRODUCTION
Silicon carbide (SiC) is widely used as a semiconductor material for next-generation power
semiconductor devices. SiC, as compared with silicon (Si), has superior physical properties
such as a higher breakdown electric field, higher thermal conductivity, lower thermal
generation rate, higher saturated electron drift velocity, and lower intrinsic carrier
concentration. These attributes realize SiC-based power semiconductor devices with faster
switching speeds, lower losses, higher blocking voltages, and higher temperature operation
relative to standard Si-based power semiconductor devices.
SiC-based power semiconductor devices are not fully realized due to some issues including
high costs, low yield, and low long-term reliability. In particular, one of the serious issues lies
in the defects existing in SiC homoepitaxial wafers. Although efforts of decreasing defects in
SiC homoepitaxial wafers are actively implemented, there are a number of defects in
commercially available SiC homoepitaxial wafers. Therefore, it is indispensable to establish
an international standard regarding the quality assessment of SiC homoepitaxial wafers.
The IEC 63068 series of standards is planned to comprise Part 1, Part 2, and Part 3, as
detailed below. This document provides definitions and guidance in use of photoluminescence
for detecting defects in commercially available silicon carbide (SiC) homoepitaxial wafers.
Part 1: Classification of defects
Part 2: Test method for defects using optical inspection
Part 3: Test method for defects using photoluminescence

SEMICONDUCTOR DEVICES –
NON-DESTRUCTIVE RECOGNITION CRITERIA OF DEFECTS
IN SILICON CARBIDE HOMOEPITAXIAL WAFER FOR POWER DEVICES –

Part 3: Test method for defects using photoluminescence

1 Scope
This part of IEC 63068 provides definitions and guidance in use of photoluminescence for
detecting as-grown defects in commercially available 4H-SiC (Silicon Carbide) epitaxial
wafers. Additionally, this document exemplifies photoluminescence images and emission
spectra to enable the detection and categorization of the defects in SiC homoepitaxial wafers.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
photoluminescence
PL
emission of light from materials as a subsequence of electronic excitation by absorption of
photons
3.2
photoluminescence imaging
PL imaging
technique for capturing, processing and analysing images of defects using light source for
electronic excitation, focusing optics, optical filter, optical image sensor and computer
systems
3.3
focusing optics
lens system used for magnifying and capturing optical images
3.4
optical filter
optical component designed to transmit only a specific wavelength region and to block other
regions
3.5
optical image sensor
device to transform an optical image into digital data

– 8 – IEC 63068-3:2020 © IEC 2020
3.6
image capturing
process of creating a two-dimensional original digital image of defects in the wafer
3.7
original digital image
digitized image acquired by an optical image sensor, without performing any image
processing
Note 1 to entry: An original digital image consists of pixels divided by a grid, and each pixel has a grey level.
3.8
charge-coupled device image sensor
CCD image sensor
light-sensitive integrated circuit chip that converts detected optical information to electrical
signals
Note 1 to entry: A CCD consists of fine elements, each of which corresponds to a pixel of original digital images.
3.9
pixel
smallest formative element of original digital images, to which a grey level is assigned
3.10
resolution
number of pixels per unit length (or area) of original digital images
Note 1 to entry: If resolutions in the X- and Y-directions are different, both values have to be recorded.
3.11
spatial resolution
ability to distinguish two closely spaced points as two independent points
3.12
grey level
degree of brightness defined in a greyscale
Note 1 to entry: Degree of brightness is usually represented as a positive integer taken from greyscale.
3.13
greyscale
range of grey shades from black to white
EXAMPLE 8-bit greyscale has two-to-the-eighth-power (= 256) grey levels. Grey level 0 (the 1st level)
corresponds to black, grey level 255 (the 256th level) to white.
3.14
image processing
software manipulation of original digital images to prepare for subsequent image analysis
Note 1 to entry: For example, image processing can be used to eliminate mistakes generated during image
capturing or to reduce image information to the essential.
3.15
binary image
image in which either 0 (black) or 1 (white) is assigned to each pixel
3.16
brightness
average grey level of a specified part of optical images

3.17
contrast
difference between the grey levels of two specified parts of optical images
3.18
shading correction
software method for correcting non-uniformity of the illumination over the wafer surface
3.19
thresholding
process of creating a binary image out of a greyscale image by setting exactly those pixels
whose value is greater than a given threshold to white and setting the other pixels to black
Note 1 to entry: To make a binary image, the grey level of each pixel in the original greyscale image is replaced
with 0 (black) or 1 (white), depending on whether the grey level is greater than or less than or equal to a given
threshold.
3.20
edge detection
method of isolating and locating edges of defects and surface features in a given digital image
3.21
image analysis
extraction of imaging information from processed digital images by software
3.22
image evaluation
process of relating a series of values resulting from image analysis of one or more
characteristic images via a classification scheme of defects
3.23
reference wafer
specified wafer used for parameter settings, which has already been evaluated for checking
the reproducibility and repeatability of optical inspection process for defects
3.24
test wafer
semiconductor wafer under test to evaluate defects
3.25
crystal direction
direction, usually denoted as [uvw], representing a vector direction in multiples of the basis
vectors describing the a, b and c crystal axes
Note 1 to entry: In 4H-SiC showing a hexagonal symmetry, four-digit indices [uvtw] are frequently used for crystal
directions.
[SOURCE: ISO 24173:2009 [1] , 3.3, modified – The original note has been replaced by a
new note to entry.]
3.26
defect
crystalline imperfection
____________
Numbers in square brackets refer to the Bibliography.

– 10 – IEC 63068-3:2020 © IEC 2020
3.27
micropipe
hollow tube extending approximately normal to the basal plane
3.28
threading screw dislocation
TSD
screw dislocation penetrating through the crystal approximately normal to the basal plane
3.29
threading edge dislocation
TED
edge dislocation penetrating through the crystal approximately normal to the basal plane
3.30
basal plane dislocation
BPD
dislocation lying on the basal plane
3.31
scratch trace
dense row of dislocations caused by mechanical damages on the substrate surface
3.32
stacking fault
planar crystallographic defect in monocrystalline material, characterized by an error in the
stacking sequence of crystallographic planes
3.33
propagated stacking fault
stacking fault propagating from substrate toward the homoepitaxial layer surface
3.34
stacking fault complex
stacking fault complex consisting of a basal plane stacking fault and a prismatic fault
3.35
polytype inclusion
volume crystal defect showing different polytypes from that of the homoepitaxial layer
3.36
particle inclusion
macroscopic size particle existing in the homoepitaxial layer
3.37
bunched-step segment
surface morphological roughness consisting of bunched-steps
3.38
surface particle
particle deposited on the epitaxial layer surface after epitaxial growth

4 Photoluminescence method
4.1 General
Defects with characteristic PL features shall be evaluated by PL method. The following
+
descriptions concern such defects in n/n -type 4H-SiC homoepitaxial wafers with an off-cut
angle of 4° along the direction of [11 2 0], where their PL images are obtained by detecting
emission wavelengths longer than 650 nm:
– individual linear defects exhibiting bright line images, e.g. BPDs;
– individual planar defects exhibiting dark contrast images, e.g. stacking faults, propagated
stacking faults, stacking fault complexes, and polytype inclusions.
When emission wavelengths from 400 nm to 500 nm are used for the defect detection,
stacking faults exhibit bright contrast images.
Defects without characteristic PL features or with weak PL contrasts against SiC area with no
defects should be evaluated by other test methods such as optical inspection and X-ray
topography. Those defects include micropipes, TSDs, TEDs, scratch traces, particle
inclusions, bunched-step segments, and surface particles.
4.2 Principle
PL images of defects are captured and transformed into a digital format. In the course of this
process, an SiC homoepitaxial wafer is irradiated with excitation light whose energy is greater
than the bandgap of 4H-SiC crystals, and the resulting PL is collected and recorded as a PL
image of a specified area of the wafer including defects. PL is detected using an optical image
sensor such as a CCD image sensor, and PL image is usually acquired using an optical filter
which transmits a specific range of PL appropriate for the detection of each type of defect.
Then, the obtained PL image (digital image) is processed by manipulating the grey levels of
the image. Through a specified scheme of image analysis, the image information is reduced
to a set of values which are specific to the detected defects.
A greyscale image is produced from the original digital image of defects in the wafer. This
image can be converted into a binary image (thresholding). The size and shape of defects are
measured, and the distribution and number of defects within a specified area of wafer are
calculated.
NOTE The size of planar and volume defects extending along the off-cut direction depends on the thickness of
homoepitaxial layer. Details of such defects and the method of estimating the size of their PL images are described
in Annex A and 4.6.2, respectively.
4.3 Requirements
4.3.1 Measuring equipment
4.3.1.1 PL imaging system
Measuring equipment for PL imaging of defects in 4H-SiC homoepitaxial wafers is shown in
Figure 1. The measuring equipment consists of light source, focusing optics, optical filter,
CCD, wafer stage, controller/processor, and dark box. Each component shall have the
performance specified below. Different wafer specifications and defect types will require an
optimum setup of light source, focusing optics and optical filter to acquire distinct PL features
that are to be analysed. Therefore, a combination of light source, focusing optics and optical
filter for a specific application needs to be prepared.

– 12 – IEC 63068-3:2020 © IEC 2020

Key
1 light source
2 excitation light
3 photoluminescence
4 focusing optics
5 optical filter
6 CCD
7 controller/processor
8 wafer stage
9 test wafer or reference wafer
10 dark box or rack housing
Figure 1 – Schematic diagram of PL imaging system
4.3.1.2 Light source
A gas discharge lamp, such as a mercury-xenon lamp, and diode lasers with a specific
emission wavelength are used as a typical source of photons for electronic excitation. When a
white light from a gas discharge lamp is used for electronic excitation, suitable optical filters
for the light source shall be used to obtain excitation light with a suitable wavelength band for
PL imaging. The suitable wavelength of excitation light shall be selected to be equal to or
greater than the bandgap energy of 4H-SiC. For example, an emission line of 313 nm or
365 nm from a mercury-xenon lamp is suitable for electronic excitation of 4H-SiC.
4.3.1.3 Objective lens
Objective lens should be selected to adjust the inspection area and the depth of focus to
eliminate the influence from wafer backside.

4.3.1.4 Optical filter
Optical filters shall be selected to suit the inspection for specified defects in homoepitaxial
wafers.
NOTE Typical PL spectra of defects are described in Annex B.
4.3.1.5 Uniformity and constancy
A combination of light source and focusing optics should be optimized to achieve sufficient
uniformity of the excitation light intensity on the wafer surface. The PL intensity at each point
on the epitaxial layer is adjusted in an appropriate range so that defects are clearly detected.
Uniformity of excitation light intensity can be achieved using hardware and/or software.
The spectral and power distributions of the excitation light are maintained constant during the
whole measurement period.
4.3.2 Wafer positioning and focusing
Wafers shall be positioned in the plane of Cartesian coordinate system (X–Y) or cylindrical
coordinate system (R–θ). The third axis (Z) is the optical axis of image capturing system.
The Z-axis is perpendicular to the plane and its point of intersection with the plane shall be
the point of focus. The distance between the front-end portion of image-capturing optics and
the wafer surface shall be constant, independent of the thickness of the wafers, so that
focusing and magnification are not mutually adversely affected.
4.3.3 Image capturing
The PL imaging system is typically composed of a light source, focusing optics, CCD image
sensor as an optical digital sensor, lighting-geometry adjustment system, wafer stage and
light-tight enclosure. A dark box or a rack housing is often used to prevent the interference by
external illumination. The spatial resolution of the PL imaging system shall be high enough to
capture distinct features of small size defects. The image information is digitized directly
within the optical image sensor unit.
To ensure the repeatability and reproducibility of the image capturing procedure, parameter
settings should be carried out at a regular interval. This can be performed using specified
reference wafers, for example, silicon or silicon carbide wafers.
4.3.4 Image processing
The image processing covers numerous features such as brightness, contrast, edge detection,
shading correction, and inversion.
Different software solutions may employ different mathematical algorithms for similar
operations, and images processed by different image-processing algorithms will not be
identical. Parameter settings, e.g. using reference wafers, are performed to ensure that
results are comparable.
4.3.5 Image analysis
Two different methods are used for image analysis: binary (black/white) analysis and grey-
level analysis. To obtain a binary image from a grey-level image, threshold procedure is used.
An appropriate algorithm should be used for image analysis to detect successfully defects in
test wafers.
– 14 – IEC 63068-3:2020 © IEC 2020
4.3.6 Image evaluation
The result of image analysis is a set of values which are pertinent to a specific application.
This set of values is transformed into one or more characteristic values via a classification
scheme of defects.
4.3.7 Documentation
Relevant parameters for PL imaging system shall be documented. These comprise:
a) wavelength of excitation light from light source;
b) wavelength range detected by optical image sensor through optical filters;
c) spatial resolution of PL imaging system.
4.4 Parameter settings
4.4.1 General
Test wafers should be compared with reference wafers.
The purpose of parameter settings is to fix the image capturing parameters in such a way that
image analysis will be possible to identify the PL features of defects in test wafers by using
reference wafers. A visual comparison is performed to confirm the correspondence between
the reference wafers and test wafers with regard to the detected defect.
The reference wafers should be as similar as possible to test wafers on the structure and
specification; thus, it is desirable to prepare both the reference wafers and test wafers in the
same laboratory or factory, using the same equipment and process.
4.4.2 Parameter setting process
Parameter settings should be executed as described below using a set of reference wafers.
Take an image of each defect on test wafer using a selected PL imaging system. The images
of defects on test wafer should be visually compared with those of reference wafers.
4.5 Procedure
Prepare test wafers for PL imaging as follows.
Create images of test wafers using a parameter-optimized PL imaging system. Once suitable
threshold values are established, a digitized image provides, on analysis, contrasts pertinent
to the defect structures.
4.6 Evaluation
4.6.1 General
In contrast to manual assessment of defects, PL imaging system can determine directly the
size and shape of defects with characteristic PL features (see 4.1 and Annex A).
The image analysis provides data that identify the positions and types of defects. The edge
exclusion of test wafers should be less than 5 mm.
4.6.2 Mean width of planar and volume defects
With the known thickness of homoepitaxial layer d, in micrometres, and an off-cut angle of 4°,
calculate the mean width parallel to the off-cut direction l, in micrometres, of planar and
volume defects except particle inclusions and surface particles using the following formula:

d
l=
tan 4°
( )
For example, values of the mean width l of defects for 10 µm- and 30 µm-thickness
homoepitaxial layers are approximately 145 µm and 430 µm, respectively.
When planar and volume defects are formed in the middle of epitaxial growth, the defect width
is less than given by the above formula.
4.6.3 Evaluation process
If the recognized objects are either extended or surface defects, the number of defects shall
be counted for each type of defect.
Defect maps, which indicate the positions (plane coordinates) of detected defects across the
entire wafer, should be formed. In the maps, the position of the orientation flat or notch of the
wafer shall also be indicated. The coordinate origin of the map should be the centre of the
circle, which corresponds to the main edges of the wafer. The horizontal axis of the
coordinate should be parallel to the primary orientation flat of the wafer.
4.7 Precision
Information on the precision of this test method is currently not available.
4.8 Test report
4.8.1 Mandatory elements
A test report shall contain the following information:
a) inspection results:
1) number of each type of defect detected by PL imaging;
b) test wafers:
1) manufacturer;
2) trade name;
3) wafer identification;
c) reference to this part of IEC 63068;
d) PL imaging system:
1) wavelength of excitation light from light source;
2) intensity of excitation light at the wafer surface;
3) wavelength range detected by optical image sensor through optical filters;
4) spatial resolution of PL imaging system;
e) date of the test.
4.8.2 Optional elements
The following information should be contained in the test report:
a) inspection results:
1) positions (plane coordinates) of all the detected defects;
2) defect maps;
b) any deviations from the procedure;
c) any unusual features observed.

– 16 – IEC 63068-3:2020 © IEC 2020
Annex A
(informative)
Photoluminescence images of defects
A.1 General
Annex A shows typical PL images and features of defects in 4H-SiC homoepitaxial wafers
(epitaxial layer thickness: 10 µm) acquired by a PL imaging system using an excitation light of
wavelength of 365 nm. A 650 nm long pass optical filter was used for detecting defects. The
pixel resolution of the images was 2 µm. In Figures Figure A.1 to Figure A.5, the subfigures in
the left and right columns denote a photoluminescence (PL) image and a schematic
illustration of the plan-view observation image of defect, respectively.
A.2 BPD
BPDs exhibit bright line contrasts in PL images when captured at emission wavelengths
longer than 650 nm.
NOTE 1 The mean width l, in micrometres, of this type of defects depends on the thickness d, in micrometres, of
the homoepitaxial layer (see 4.6.2).
NOTE 2 The extension directions of BPDs are predominantly parallel or nearly parallel to the step flow direction.
However, BPDs also often extend in other directions and can be curved.

a) Example 1 of BPD: PL image b) Example 1 of BPD: Schematic illustration

c) Example 2 of BPD: PL image d) Example 2 of BPD: Schematic illustration
Key
1 BPD
Figure A.1 – BPD
A.3 Stacking fault
Stacking faults exhibit characteristic features in PL images of 4H-SiC homoepitaxial wafers.
They exhibit characteristic PL spectra depending on their stacking sequences.
NOTE 1 The types of stacking faults can be distinguished by examining their emission spectra.
NOTE 2 Three types of Frank-type stacking faults are detected in the visible wavelength range at room
temperature [see Figure B.2].
NOTE 3 Four types of Shockley-type stacking faults are detected in the visible wavelength range at room
temperature [see Figure B.3].
NOTE 4 The mean width l, in micrometres, of this type of defects depends on the thickness d, in micrometres, of
homoepitaxial layer (see 4.6.2).

– 18 – IEC 63068-3:2020 © IEC 2020

a) Example of stacking fault: b) Example of stacking fault:
PL image Schematic illustration

Figure A.2 – Stacking fault
A.4 Propagated stacking fault
This is a stacking fault in a homoepitaxial layer formed by inheriting a stacking fault in a
substrate. Propagated stacking faults exhibit the PL features determined by their stacking
sequences, as illustrated in Clause A.3.
NOTE 1 The mean width l, in micrometres, of this type of defects depends on the thickness d, in micrometres, of
homoepitaxial layer (see 4.6.2).
NOTE 2 These defects are often referred to as "bar-shaped stacking fault".

a) Example of propagated stacking fault: b) Example of propagated stacking fault:
PL image Schematic illustration

Figure A.3 – Propagated stacking fault

A.5 Stacking fault complex
Stacking fault complexes exhibit characteristic features in PL images of 4H-SiC homoepitaxial
wafers: for example, dark acicular (needle-shaped) morphological features extending along
the off-cut direction when captured at emission wavelengths longer than 650 nm.
NOTE 1 Stacking fault complexes exhibit bright contrast images when captured at emission wavelength of 420 nm,
which originates from their stacking sequence similar to a Frank-type stacking fault (extrinsic) (see Figure B.5).
NOTE 2 The mean width l, in micrometres, of this type of defects depends on the thickness d, in micrometres, of
homoepitaxial layer (see 4.6.2).
NOTE 3 These defects are often referred to as "carrot defect".

a) Example of stacking fault complex: b) Example of stacking fault complex:
PL image Schematic illustration

Figure A.4 – Stacking fault complex
A.6 Polytype inclusion
Polytype inclusions exhibit characteristic PL features on the 4H-SiC homoepitaxial layer
surface: for example, dark triangles of various shapes extending along the off-cut direction
when captured at emission wavelengths longer than 650 nm.
NOTE 1 Polytype inclusions exhibit bright contrast images when captured at emission wavelengths between
500 nm and 600 nm (see Figure B.6).
NOTE 2 The mean width l, in micrometres, of this type of defects depends on the thickness d, in micrometres, of
homoepitaxial layer (see 4.6.2).
NOTE 3 These defects are formed not only due to particles, which is the case shown in Figure A.5, but also due
to other causes such as mechanical surface damage as a result of the polishing process.
NOTE 4 These defects are often referred to as "triangular inclusion", "triangular defect", or "comet tail defect".

– 20 – IEC 63068-3:2020 © IEC 2020

a) Example of polytype inclusion: b) Example of polytype inclusion:
PL image Schematic illustration
Key
1 particle
Figure A.5 – Polytype inclusion

Annex B
(informative)
Photoluminescence spectra of defects
B.1 General
Annex B shows typical PL spectra obtained at room temperature from defects which have
characteristic PL features. PL spectra were obtained by using a spectrometer with focal length
of 32 cm. The 325 nm line of a He-Cd laser was used as an excitation source. PL was
dispersed by the spectrometer with a grating of 150 lines per millimetre and detected by a
CCD detector. The laser beam was guided into a microscope and focused through an
objective lens. The laser beam is focused to a spot size of about 2 µm on the sample surface
2 2
with a power density of 30 kW/cm to 100 kW/cm .
B.2 BPD
The "difference between with and without B
...