Pis’ma v ZhETF, vol. 112, iss. 3, pp. 172 - 173
© 2020 August 10
Microstructure and formation mechanism of V-defects in the
InGaN/GaN multiple quantum wells with a high in content
H. Wang+1), Q. Tan+∗, X. He+
+Academy of Electronic Information and Electrical Engineering, Xiangnan University, 423000 Chenzhou, China
∗Institute of Physics and Information Science, Hunan Normal University, 410081 Changsha, China
Submitted 2 June 2020
Resubmitted 19 June 2020
Accepted 19
June 2020
DOI: 10.31857/S1234567820150057
InGaN/GaN heterostructures and multi-quantum
wall layers were epitaxially grown successively on the
well (MQW) structures have a wide range of appli-
six {1011} planes (marked with “s-QW”). The InGaN
cations such as the active layers in GaN-based light-
and GaN sidewall layers forming by the layer-by-layer
emitting diodes [1] as it is possible to tune the optical
growth similar to that on the (0001) planes (marked
band gap from visible to ultraviolet spectral range by
with “c-QW”). Because the thin InGaN layer is sepa-
controlling the In composition [2]. However, the initial
rated from the thin GaN layer, having almost the same
GaN layer is usually grown on a sapphire substrate, and
composition with the main In0.20Ga0.80N MQW, they
the high lattice mismatch between substrate and epi-
might also work as another MQW, emitting undesirable
layer leads to highly defective material with high den-
long-wavelength weak extra lights. Therefore, the entire
sities of threading dislocations (TD). These defects af-
MQW has the (0001) surface and the {1011} surfaces
fect the structural and optical quality of the active layer
during the MQW deposition. The angle of connecting
composed of the InGaN/GaN MQW structure [3]. The
the (1011) interface (or the (1011) interface) with the
so-called V-defects have been frequently observed in the
(0001) interface are not sharp (about an angle of 118◦),
InGaN/GaN MQW [4-6]. The origin of these defects
but this corner is curved, as seen in Fig. 1.
and the role they play on the optical emission are still
not clear though there are some studies focused on this
issue [3, 4, 7].
All layers of this sample were grown on a c-sapphire
(0001) substrate by using metal-organic chemical va-
por deposition (MOVCD). Trimethylgallium (TMGa),
trimethylindium (TMIn), and ammonia (NH3) were
used as the source precursors for Ga, In, and N, re-
spectively. After thermal cleaning of the substrates in
hydrogen ambient for 10 min at 1100◦C, a 25 nm thick
GaN nucleation layer was deposited at 550◦C. Subse-
quently, an undoped GaN (u-GaN) layer and a n-type
doped GaN (n-GaN) layer were grown on the low tem-
perature GaN/sapphire at 1050◦C for 2 h with a V/III
Fig. 1. Dark-field HRTEM images of V-defects in the
flux ratio of 1500. The InGaN/GaN MQW is composed
InGaN/InGaN MQW
of fifteen periods of 3 nm In0.20Ga0.80N nominal com-
position wells and 13 nm GaN barriers. Finally, a GaN
capping layer was deposited on the MQW.
The InGaN and GaN crystals were formed by the
The TEM diagram in Fig. 1 shows that the V de-
layer-by-layer growth on the (0001) and {1011} sur-
fect begins at a TD, which runs through MQW from
faces, where each monolayer on these surfaces would
the high temperature GaN layer to the capping layer.
extend from the distant nucleation site toward the edge
During the MWQ deposition, the InGaN and GaN side-
through the supply of atoms that adhere and migrate on
the surface. With the growth of monolayers, the supply
1)e-mail: whycs@163.com
of atoms on both the (0001) and {1011} surfaces may be
172
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