Topic
Band offset
About: Band offset is a research topic. Over the lifetime, 2446 publications have been published within this topic receiving 53450 citations.
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TL;DR: In this article, the dependence of the active layer structure on the performance of the deep-UV AlGaN light-emitting diodes was theoretically investigated with an APSYS simulation program.
Abstract: The dependence of the active-layer structure on the performance of the deep-UV AlGaN light-emitting diodes (LEDs) was theoretically investigated with an APSYS simulation program. Several structure parameters such as well width, well number, barrier height, barrier width, and doping type were employed to study how these parameters change the band structures as well as the carrier distributions. The band offset and bowing parameter used in the theoretical analysis were extracted from the experimental results. Theoretical analysis shows that the nonuniform carrier distributions as well as the low hole concentrations, which caused by polarization-induced tilted band structures, play important roles in improving the performance of the AlGaN LEDs. Compensating this asymmetric band structure and increasing the hole density are the important keys to improve the AlGaN LED performance. Numerical simulation results suggest that the higher output power can be obtained when the active layer consists of only one quantum well with a width of 1-3 nm and two thicker n-doped barriers with a small Al composition
38 citations
TL;DR: In this paper, the authors derived the energy band profiles of as-evaporated ZrO 2 /Si(100) and annealed Zr O 2/SiO x :Zr/Si (100) systems from the onset of the energy loss spectra of O1s photoelectrons.
38 citations
TL;DR: In this paper, the optical properties of ZnSe-ZnSxSe1-x strained-layer superlattices (SLSs) are described and compared with the theoretical predictions of lattice dynamic models for multilayer structures.
38 citations
TL;DR: In this paper, the authors reported first-principles band structure calculations that show that ZnSe/CuInSe2 has a significant valence band offset (VBO, ΔEv): 0.70±0.05 eV for the relaxed interface and 0.60± 0.05eV for coherent interface.
Abstract: We report first‐principles band structure calculations that show that ZnSe/CuInSe2 has a significant valence band offset (VBO, ΔEv): 0.70±0.05 eV for the relaxed interface and 0.60±0.05 eV for the coherent interface. These large values demonstrate the failure of the common anion rule. This is traced to a stronger Cu,d‐Se,p level repulsion in CuInSe2 than the Zn,d‐Se,p repulsion in ZnSe. The VBO was then studied by synchrotron radiation soft x‐ray photoemission spectroscopy. ZnSe overlayers were sequentially grown in steps on n‐type CuInSe2(112) single crystals at 200 °C. In situ photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the In 4d and Zn 3d core lines. Results of these measurements reveal that the VBO is ΔEv=0.70±0.15 eV, in good agreement with the first‐principles prediction.
38 citations
TL;DR: In this article, the authors proposed a secondary barrier that results from the conduction band offset between CIGS and the commonly employed CdS window layer, which produces a second diode with the same polarity and in series with the primary photodiode.
Abstract: CIGS solar cells in many cases show a failure of light/dark superposition of their current-voltage (J-V) curves. Such failure generally becomes more pronounced at lower temperatures. J-V measurements under red light may also show an additional distortion, known historically as the “red kink”. The proposed explanation is that a secondary barrier results from the conduction band offset between CIGS and the commonly employed CdS window layer. This barrier produces a second diode with the same polarity and in series with the primary photodiode. The secondary-diode barrier height is modified by photoinduced changes of trap occupancy in the CdS layer, hence creating a voltage shift between dark and light conditions. Numerical modeling of the proposed explanation, including a band offset consistent with experimental and theoretical values, gives a very good fit to measured light and dark J-V curves over a wide temperature range. It also predicts the observed difference between illuminated J-V curves with photon energy above the CdS band gap, and those with sub-band-gap illumination.
38 citations