Temperature-dependent continuous-excitation and time-resolved photoluminescence
are studied to probe carrier localization and recombination in nearly
strain-balanced m-plane In0.09Ga0.91N/Al0.19Ga0.81N multi-quantum wells grown
by plasma-assisted molecular-beam epitaxy. An average localization depth of
21 meV is estimated for the undoped sample. This depth is much smaller than
the reported values in polar structures and m-plane InGaN quantum wells. As
part of this study, temperature and magnetic field dependence of time-resolved
photoluminescence is performed. At 2 K, an initial fast decay time of 0.3 ns is
measured for both undoped and doped structures. The undoped sample also
exhibits a slow decay component with a time scale of 2.2 ns. The existence of two
relaxation paths in the undoped structure can be attributed to different localization
centers. The fast relaxation decays are relatively insensitive to external
magnetic fields, while the slower relaxation time constant decreases significantly
with increasing magnetic fields. The fast decay time scale in the undoped sample
is likely due to indium fluctuations in the quantum well. The slow decay time may
be related to carrier localization in the barriers. The addition of doping leads to a
single fast decay time likely due to stronger exciton localization in the InGaN
quantum wells.
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Novel nitride quantum structures for infrared sensing
Band structure, strain, and polarization engineering of nitride heterostructures open unparalleled opportunities for quantum sensing in the infrared. Intersubband absorption and photoluminescence are employed to correlate structure with optical properties of nonpolar strain-balanced InGaN/AlGaN nanostructures grown by molecular-beam epitaxy. Mid-infrared intersubband transitions in m-plane (In)AlxGa1-xN/In0.16Ga0.84N (0.19x0.3) multi-quantum wells were observed for the first time in the range of 3.4-5.1 μm (244-360 meV). Direct and attenuated total-reflection infrared absorption measurements are interpreted using structural information revealed by high-resolution x-ray diffraction and transmission electron microanalysis. The experimental intersubband energies are better reproduced by calculations using the local-density approximation than the Hartree-Fock approximation for the exchange-correlation correction. The effect of charge density, quantum well width, and barrier alloy composition on the intersubband transition energy was examined to evaluate the potential of this material for practical infrared applications.
Temperature-dependent continuous-wave and time-resolved photoluminescence (TRPL) measurements are also investigated to probe carrier localization and recombination in m-plane InGaN/AlGaN quantum wells. Average localization depths of 21 meV and 40 meV were estimated for the undoped and doped structures, respectively. Using TRPL, dual localization centers were identified in undoped structures, while a single type of localization centers was found in doped structures. At 2 K, a fast decay time of approximately 0.3ns was measured for both undoped and doped structures, while a longer decay time of 2.2 ns was found only for the undoped sample. TRPL in magnetic field was explored to examine the effect of doping sheets on carrier dynamics.
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- Award ID(s):
- 2004462
- NSF-PAR ID:
- 10325265
- Editor(s):
- Razeghi, Manijeh; Khodaparast, Giti A.; Vitiello, Miriam S.
- Date Published:
- Journal Name:
- Proc. SPIE 12009, Quantum Sensing and Nano Electronics and Photonics XVIII
- Page Range / eLocation ID:
- 39
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Mid-infrared intersubband transitions in strain-balanced m-plane (In)AlxGa1-xN/In0.16Ga0.84N (0.19≤x≤0.3) multi-quantum wells are reported for the first time in the range of 3.4–5.1 µm (244–360 meV). Direct and attenuated total-reflection infrared absorption measurements are interpreted using structural information revealed by high-resolution x-ray diffraction and transmission electron microanalysis. The experimental intersubband energies are better reproduced by calculations using the local-density approximation than the Hartree-Fock approximation for the exchange-correlation correction. The effect of charge density, quantum well width, and barrier alloy composition on the intersubband transition energy is also investigated to evaluate the potential of this material for practical device applications.
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Differential carrier lifetime measurements were performed on c-plane InGaN/GaN single quantum well (QW) light-emitting diodes (LEDs) of different QW indium compositions as well as with and without doped barriers. Mg-doped p-type and Si-doped n-type barriers close to the QW were used to reduce the net internal electric field in the QW, thereby improving the electron–hole wavefunction overlap on the LEDs. LEDs with doped barriers show short lifetimes and low carrier densities in the active region compared to the reference LEDs. The recombination coefficients in the ABC model were estimated based on the carrier lifetime and quantum efficiency measurements. The improvement in the radiative coefficients in the LEDs with doped barriers coupled with the blueshift of the emission wavelengths indeed indicates an enhancement in wavefunction overlap and a reduction of quantum confined Stark effect as a result of the reduced internal electric field. However, doped barriers also introduce non-radiative recombination centers and thereby increase the Shockley–Read–Hall (SRH) coefficient, although the increment is less for LEDs with high indium composition QWs. As a result, at high indium composition (22%), LEDs with doped barriers outperform the reference LEDs even though the trend is reversed for LEDs with lower indium composition (13.5%). Despite the trade-off of higher SRH coefficients, doped barriers are shown to be effective in reducing the internal electric field and increasing the recombination coefficients.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1117/12.2608173
