The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔEc = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence spectrum. In the entire temperature range under study, T = 290 – 480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated on the large the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the electroluminescence intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290 – 345 K, and a linear increase is observed at T < 345 K. Theoretical calculations have shown that this behavior of the temperature dependence of the optical power caused by competition between the radiative recombination, thermionic emission and Auger recombination.
Maya Mikhailova, Edward Ivanov, Leonid Danilov, Andrei Petukhov, Karina Kalinina, Nikolai Stoyanov, Yuri Yakovlev, Alice Hospodková, Jiri Pangrác, Jiri Oswald, Marketa Ziková, Edward Hulicius
We report on superlinear electroluminescent structures based on AlSb/InAs1-xSbx/AlSb deep quantum well grown by
MOVPE on n-GaSb:Te substrate. Dependence of the electroluminescence (EL) spectra and optical power on the drive
current in nanoheterostructures with AlSb/InAs1-xSbx/AlSb quantum well at 77 – 300 K temperature range was studied.
Intensive two-band superlinear EL in the 0.5 - 0.8 eV photon energy range was observed. Optical power enhancement
with the increasing drive current at room temperature is caused by the contribution of the additional electron-hole pairs
due to the impact ionization by the electrons heated at the high band offset between AlSb and the first electron level Ee1
in the InAsSb QW. Study of the EL temperature dependence at 90 – 300 K range enabled us to define the role of the first
and second heavy hole levels in the radiative recombination process. It was shown that with the temperature decrease,
the relation between the energies of the valence band offset and the second heavy hole energy level changes due to the
temperature transformation of the energy band diagram. That is why the EL spectrum revealed radiative transitions from
the first electron level Ee1 to the first hole level Eh1 in the whole temperature range (90 – 300 K) while the emission band
related with the transitions to the second hole level occurred only at T < 200 K.
M. Mikhailova, G. Zegrya, L. Danilov, E. Ivanov, K. Kalinina, N. Stoyanov, Kh. Salikhov, Yu. Yakovlev, E. Hulicius, A. Hospodkova, J. Pangrac, M. Zikova
We report on the observation of superlinear electroluminescence in nanoheterostructures based on GaSb with a deep
narrow Al(As)Sb/InAsSb/Al(As)Sb quantum well in the active region, grown by metal organic vapor phase epitaxy.
Electroluminescence spectra for different driving currents were measured at temperatures of 77 and 300 K. It is shown
that such structure exhibits superlinear dependence of optical power on the drive current and its increase of 2-3 times in the current range 50-200 mA. This occurs due to impact ionization in the Al(As)Sb/InAsSb quantum well in which a
large band offset at the interface ΔEC = 1.27 eV exceeds ionization threshold energy for electrons in the narrow-gap well. Theoretical calculation of the size quantization energy levels is presented, and possible cases of impact ionization, depending on the band offset ΔEC at the interface and on the quantum well width, are considered. This effect can be used to increase quantum efficiency and optical power of light emitting devices (LEDs, lasers) operating in mid-infrared spectral range, as well as for photovoltaic elements.
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