Growth and characterization of (InSb)
m
(InP)
n
short period superlattices
T. Utzmeier,
a)
G. Armelles, P. A. Postigo, and F. Briones
Instituto de Microelectro ´nica de Madrid, CSIC, Isaac Newton 8, 28760 Tres Cantos, Spain
P. Castrillo
Departamento E. y Electro ´nica, Dr. Mergelina s/n, 47011 Valladolid, Spain
A. Sanz-Hervas, M. Aguilar, and E. J. Abril
b)
Departamento Tecnologı ´a Electro ´nica, ETSIT, Ciudad Universitaria, 28040 Madrid, Spain
Received 25 November 1996; accepted for publication 3 April 1997
Short period superlattices of (InSb)
m
(InP)
n
were grown on semi-insulating 001 InP substrates by
atomic layer molecular beam epitaxy. High resolution x-ray diffractometry was used to study the
structural quality of the superlattices. Raman spectroscopy, in conjunction with theoretical
calculations, provided information about intermixing at the interfaces. © 1997 American Institute
of Physics. S0003-69519702422-4
Renewed interest in narrow band gap III–V semiconduc-
tors like InSb, InAs, or InAsSb has come up in the recent
years. These materials are especially interesting for high per-
formance, optoelectronic applications in the infrared up to 12
m Ref. 1 and for magnetic field sensors. Heterostructures
based on InSbP would be very useful for quantum well la-
sers, detectors,
2
and two-dimensional electron-gas devices.
3
Since InSb
x
P
1 -x
, exhibits severe growth problems,
4
how-
ever, we studied the growth of short period strained layer
superlattices SPSLs as alternative materials that could re-
place the ternary alloys. Nevertheless, the growth of such
InSb/InP SPSLs could be, in principle, regarded to be chal-
lenging due both to the extremely high lattice mismatch
about 10% between InSb and InP and to the possible inter-
mixing at the interfaces
5,6
that may be intensified in this case
by the incorporation competition between the group-V
elements.
7
In this letter we report on the successful growth of
high quality InSb/InP SPSLs. A Raman study was performed
in order to investigate the Sb–P intermixing in these super-
lattices.
Samples were grown by atomic layer molecular beam
epitaxy ALMBE
8
in an otherwise conventional, solid-
source MBE system on semi-insulating 001 InP substrates.
Typical beam equivalent pressures were 1.5– 3 10
-6
Torr
for both materials in the atomic layer pulsed operation mode.
After oxide desorption at 490 °C under P
2
flux, the superlat-
tices were grown at 380 °C without an intermediate buffer
layer. The total thicknesses of all layers are between 0.32 and
0.8 m using a growth velocity of 0.5 monolayers/s. The
stoichiometric layer composition was controlled in situ by
means of reflectance difference RD measurements of the
In-dimer coverage fraction,
9
and the surface reconstruction
was controlled by reflection high energy electron diffraction
RHEED. After growth the samples were cooled down un-
der Sb pressure until 300 °C, from thereon no desorption
could be observed.
We grew various (InSb)
m
(InP)
n
SPSLs with equivalent
mean compositions close to those of InP and InSb, respec-
tively, with ( m , n ) equal to 1,15, 15,1, 10,1, 8,1, and
4,1. For the Sb-rich compositions, i.e., where the InSb lay-
ers are thicker than the InP layers in the superlattice and,
therefore, are also thicker than 1 monolayer ML, we ob-
served a transition from a two-dimensional growth mode to
three-dimensional island growth that was confirmed by a
spotty RHEED pattern within the second InSb layer. This
island growth occurs after about 1.1 ML. After further super-
lattice growth of approximately 200 Å the RHEED pattern
progressively turned streaky again, indicating the recovery of
a plane growth front. For the InP-rich samples this growth
mode transition was not observed, because the InSb layer
thickness here was limited to 1 ML, which is less than the
critical thickness for this transition.
All the samples were studied by high resolution x-ray
diffractometry HRXRD and Raman spectroscopy. HRXRD
/2 scans were carried out in a Bede D
3
diffractometer in
the high intensity mode, measuring the symmetric 004, 002,
and the asymmetric 115 reflections. Figure 1 shows the 004
reflections of samples InSb
15
InP
1
and InSb
1
InP
15
. In
sample InSb
15
InP
1
up to forth order satellites can be
clearly seen, thus allowing accurate determination of the pe-
riod thickness and average Sb content. In sample
InSb
1
InP
15
only second order satellites can be distin-
guished, mainly due to the lower total thickness of the SPSL
and the lower Sb content. The other samples, except
a
Electronic mail: thomas@imm.cnm.csic.es
b
Present address: ETSIT, Real de Burgos, 47011 Valladolid, Spain.
FIG. 1. HRXRD measurements and simulations of samples InSb
15
InP
1
bottom and InSb
1
InP
15
top taken from the 004 reflection. Satellite
peaks up to fourth order around the 0-order peak can be observed.
3017 Appl. Phys. Lett. 70 (22), 2 June 1997 0003-6951/97/70(22)/3017/3/$10.00 © 1997 American Institute of Physics
Downloaded¬30¬Aug¬2010¬to¬161.111.180.103.¬Redistribution¬subject¬to¬AIP¬license¬or¬copyright;¬see¬http://apl.aip.org/about/rights_and_permissions