Results 1 - 10 of 1128
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[en] This paper reports on the unipolar medium wavelength infrared (MWIR) InAs/GaSb/B–Al0.2Ga0.8Sb type-II superlattice (T2SL) nBn detector's photoelectrical performance. In our model, the heterojunction barrier-active region (absorber) was assumed to be decisive as the contributing dark current mechanism limiting nBn's detector performance. The voltage drop analysis on the nBn structure was introduced to estimate the bias drop on the heterojunction barrier-active region. It was assumed that the contact n+-barrier heterojunction's layer has an insignificant influence on the electrical properties of the detector. In addition, a bulk-based model with an effective band gap of T2SL material has been assumed in the device modeling. Both current–voltage (I–V) and differential resistance–area product RA(V,T), characteristics of nBn's detector were found to be dominated by diffusion and generation–recombination currents in the zero-bias and the low-bias regions. At medium values of reverse voltages, the dark current was mostly affected by trap-assisted tunneling, whereas the band-to-band tunneling revealed its contribution at high values of reverse bias (V > 0.7 V). The RA(V,T) characteristics' fitting procedure allowed estimation of both diffusion and generation–recombination lifetimes as well as the trap energy level temperature dependence within T2SL energy gap. It was predicted that at T = 77 K, the RA product and detectivity reached values of 1000 Ωcm2 and 4 × 1011 cm Hz1/2 W-1, respectively. The corresponding values at room temperature were 0.01 Ωcm2 and D* = 5 × 108 cmHz1/2 W−1, respectively. Finally, InAs/GaSb/B–Al0.2Ga0.8Sb T2SLs nBn's state of the art was compared to the performance of InAs/GaSb T2SLs PIN photodiodes and the HgCdTe bulk photodiodes operated at near-room temperature. It was shown that the RA product of the MWIR T2SLs nBn detector has reached a comparable level with the state of the art of the HgCdTe bulk photodiodes. (paper)
[en] The conventional lifetime setup was used to study Czochralski grown unintentionally p- and n- type ([n] ≈ 6 × 1017cm−3) GaSb bulk samples. Several approaches were used to analyze the data. However, it was not possible to successfully analyze the obtained spectrums with the conventional trapping model. From the analyzed data it was derived that the reason for p-type behavior of GaSb was not VGa. Additionally, the role of gallium vacancy was studied and it's effect to lifetime values are shortly discussed.
[en] Different diffusion sources were used to study Zn diffusion in n-GaSb. We found that the Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface diffusion fronts in Zn profiles, thus converting the kink-and-tail-shaped profile to the box-shaped profile. Our analysis demonstrated that both the surface and the tail regions in the kink-and-tail profiles showed high-quality regularities. The analysis also revealed that the formation mechanism of the box profiles is the same as that of the tail region of the kink-and-tail profiles. The similarities of the photoluminescence signals between the main region of the box profiles and the tail region of the kink-and-tail profiles substantiated our findings. (paper)
[en] Electromodulation spectroscopy (photoreflectance and electroreflectance) is an excellent technique to study optical transitions in quantum well (QW) structures but the development of this technique in the midinfrared spectral region is still limited due to various reasons. In this work we report our recent progress in the development of contactless electroreflectance spectroscopy in midinfrared and discuss some aspects and perspectives of this technique in the context of its application to study optical transitions in GaSb-based QWs. Especially, we have focused on the band offset issue in GaInAsSb/GaSb QWs since the accurate study/verification of band gap discontinuities at QW interfaces is a crucial point in the optimization of laser structures grown on GaSb substrate and operating in the 1.8-3.0 μm spectral range.
[en] In this paper, we show that the growth of III-antimonides can occur via self-catalysis using either group III metal or Sb clusters at their tips. Specific experiments using GaSb and InSb systems show that bulk nucleation and growth of the respective antimonide wires can also occur from mm-sized droplets. The role of equilibrium solubility and the size of the droplet on bulk nucleation versus tip-led growth is discussed
[en] We present a multi-segment photonic crystal coupled cavity laser device on GaSb with a microstructured internal photodiode. This monolithically integrated power monitor is added as a third segment to a coupled cavity laser and is separated from the active device by six rows of two-dimensional photonic crystals, acting as highly reflecting mirrors. There is no additional fabrication step needed to integrate this feature into the coupled cavity laser, resulting in a highly integrated laser device of only 800 μm length. The device with lasing wavelength around 1955 nm shows single mode emission over a tuning range of as large as 16 nm and exhibits output powers of up to 9 mW
[en] The Ising model on a β -tin structure has a phase diagram containing three distinct phases involving order, disorder, and a frustrated ordering. The x-ray crystallographic observation that no ordered β -tin phases exist at room temperature in compound semiconductors may indicate either 'paramagnetic' (dynamic) or frustrated (static) disorder. Density functional pseudopotential calculations determine which regimes real materials fall into and predict that in materials such as GaSb, there may be two temperature-driven transitions between β -tin structures: from ordered, to frustrated order, to disordered
[en] In this work the wavelength range of GaSb-based buried tunnel junction vertical-cavity surface-emitting lasers (VCSELs) has been extended using type-II quantum wells. The developed VCSELs emit up to 4 um and operate in continuous-wave (CW) and pulsed mode until -7°C and 45°C, respectively. The maximum single-mode CW output power is 0.175 mW. A mode-hop free electro-thermal tuning of ~19 nm is achieved. These first of a kind VCSELs are highly promising for gas sensing applications.