In this study, we propose designs of an interband cascade laser (ICL) active region able to emit in the application-relevant mid infrared (MIR) spectral range and to be grown on an InP substrate. ...This is a long-sought solution as it promises a combination of ICL advantages with mature and cost-effective epitaxial technology of fabricating materials and devices with high structural and optical quality, when compared to standard approaches of growing ICLs on GaSb or InAs substrates. Therefore, we theoretically investigate a family of type II, "W"-shaped quantum wells made of InGaAs/InAs/GaAsSb with different barriers, for a range of compositions assuring the strain levels acceptable from the growth point of view. The calculated band structure within the 8-band k·p approximation showed that the inclusion of a thin InAs layer into such a type II system brings a useful additional tuning knob to tailor the electronic confined states, optical transitions' energy and their intensity. Eventually, it allows achieving the emission wavelengths from below 3 to at least 4.6 μm, while still keeping reasonably high gain when compared to the state-of-the-art ICLs. We demonstrate a good tunability of both the emission wavelength and the optical transitions' oscillator strength, which are competitive with other approaches in the MIR. This is an original solution which has not been demonstrated so far experimentally. Such InP-based interband cascade lasers are of crucial application importance, particularly for the optical gas sensing.
The optical gain spectrum has been investigated theoretically for various designs of active region based on InAs/GaInSb quantum wells-i.e., a type II material system employable in interband cascade ...lasers (ICLs) or optical amplifiers operating in the mid-infrared spectral range. The electronic properties and optical responses have been calculated using the eight-band k·p theory, including strain and external electric fields, to simulate the realistic conditions occurring in operational devices. The results show that intentionally introducing a slight nonuniformity between two subsequent stages of a cascaded device via the properly engineered modification of the type II quantum wells of the active area offers the possibility to significantly broaden the gain function. A-3 dB gain width of 1 µm can be reached in the 3-5 µm range, which is almost an order of magnitude larger than that of any previously reported ICLs. This is a property strongly demanded in many gas-sensing or free-space communication applications, and it opens a way for a new generation of devices in the mid-infrared range, such as broadly tunable single-mode lasers, mode-locked lasers for laser-based spectrometers, and optical amplifiers or superluminescent diodes which do not exist beyond 3 µm yet.
We propose designs for the active region of an interband cascade laser by utilizing a combination of In(As,Sb) and (Ga,In)(As,Sb) materials in a type-II system for strain control and to eventually ...make the entire quantum well lattice-matched to GaSb or InAs substrates. Our k · p modelling results revealed that the tuning ranges for the oscillator strength of the optical transitions and the emission wavelength are beyond what is accessible with the commonly used strained system of InAs/GaInSb. Such a solution, combined with modifications in the passive device sections, can lead to the design and fabrication of a new class of fully unstrained devices operating in the mid-infrared range.
Two designs of active region for an interband cascade laser, based on double or triple GaInSb/InAs type II quantum wells (QWs), were compared with respect to passive mode-locked operation in the ...mid-infrared range around 4 µm. The layer structure and electron and hole wavefunctions under external electric field were engineered to allow controlling the optical transition oscillator strength and the resulting lifetimes. As a result, the investigated structures can mimic absorber-like and gain-like sections of a mode-locked device when properly polarized with opposite bias. A significantly larger oscillator strength tuning range for triple QWs was experimentally verified by Fourier-transform photoreflectance.
Bibliography
Materials from the 43rd International School and Conference on Semiconductor Physics “Jaszowiec 2014,” Wisła, 7-12 June 2013.
Bibliogr.
Materiały z 43 Międzynarodowej Szkoły i ...Konferencji na temat Fizyki Półprzewodników "Jaszowiec 2014', Wisła, 7-12 czerwca 2013.
Bibliography
Materials from the 42nd “Jaszowiec” International School and Conference on the Physics of Semitors, Wisła, June 22-27, 2013
Bibliogr.
Materiały z 42nd "Jaszowiec" International School ...and Conference on the Physics of Semiconductors, Wisła, 22-27 czerwca 2013 r.
The effect of interface intermixing in W-design GaSb/AlSb/InAs/Ga
0.665
In
0.335
As
x
Sb
1 − x
/InAs/AlSb/GaSb quantum wells (QWs) has been investigated by means of optical spectroscopy supported by ...structural data and by band structure calculations. The fundamental optical transition has been detected at room temperature through photoluminescence and photoreflectance measurements and appeared to be blueshifted with increasing As content of the GaInAsSb layer, in contrast to the energy-gap-driven shifts calculated for an ideally rectangular QW profile. The arsenic incorporation into the hole-confining layer affects the material and optical structure also altering the InAs/GaInAsSb interfaces and their degree of intermixing. Based on the analysis of cross-sectional transmission electron microscopy images and energy-dispersive X-ray spectroscopy, we could deduce the composition distribution across the QW layers and hence simulate more realistic confinement potential profiles. For such smoothed interfaces that indicate As-enhanced intermixing, the energy level calculations have been able to reproduce the experimentally obtained trend.
•Electronic structure calculations of GaSb-based type II active region of long wavelength interband cascade lasers.•Study of electric field effect on the optical transitions in long wavelength ...W-design quantum wells.•Optimization of the emission wavelength and type II transition intensity for structures emitting in the range up to 12μm.
In this paper, we present theoretical investigation of the band structure properties of the type-II W-design AlSb/InAs/GaInSb/InAs/AlSb quantum wells predicted for the active region of interband cascade lasers emitting in a broad range of mid infrared. We utilize the multiband k·p theory in order to calculate the dependence of the energy and oscillator strength of the fundamental optical transition on the thickness of particular layers confining electrons and holes, including the external bias to simulate the conditions occurring in an operational device. It is shown that for a given electric field the properly chosen thicknesses of the wells allow optimizing simultaneously the emission wavelength and type II transition intensity for any wavelength up to about 12μm at least.
We present an experimental study on optical properties and dynamics of direct and spatially and momentum indirect excitons in AlGaAs/AlAs quantum wells near the crossover between \(\varGamma\)- and ...\(X\)-valley confined electron states. The time-integrated photoluminescence experiment at \(T=\)4.8 K revealed three simultaneously observed optical transitions resulting from (a) a direct exciton recombination, involving an electron and a hole states both located in the \(\varGamma\)-valley in the quantum well layer, and (b) two spatially and momentum indirect excitons, comprising of the confined electron states in the \(X\)-valley in the AlAs barrier with different effective masses and quantum well holes in the \(\varGamma\)-valley. The measured spatial extent, density dependence and temperature dependence of the structure photoluminescence revealed characteristics necessary to pinpoint the states' nature and provided their characterization crucial in future device design. Temporal dynamics observed in the time-resolved photoluminescence measurement showed the complexity of the capture and recombination dynamics, largely affected by nonradiative processes, what is additionally critical in the system's use. This solid state platform hosting both direct and indirect excitons in a highly tunable monolithic system can benefit and underline the operation principles of novel electronic and photonic devices.
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