2007 Fiscal Year Final Research Report Summary
Study of the Optical Processes in Nitride Alloy Semiconductors
| Project/Area Number |
18540320
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics I
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| Research Institution | Wakayama University |
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Principal Investigator |
SHINOZUKA Yuzo Wakayama University, Faculty of Systems Engineering, Professor (30144918)
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| Co-Investigator(Kenkyū-buntansha) |
UNO Kazuyuki Wakayama University, Faculty of Systems Engineering, Associate Professor (90294305)
KAN'NO Ken'ichi Wakayama University, Faculty of Systems Engineering, Professor (80024339)
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| Project Period (FY) |
2006 – 2007
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| Keywords | alloy semiconductor / superlattice / quantum well / III-V compound / CPA / ESR / exciton / nitride |
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| Research Abstract |
1. The optical absorption spectrum of a binary alloy semiconductor A_<1-x>B_x were studied by coherent potential approximation (CPA) . A tight binding model is used for a Frenkel exciton in the presence of the diagonal and off-diagonal randomness. The effects of the randomness are respectively included as the potential part Σ (E) and the amplitude part Γ(E), which are shown to relate to the coherent locator L (E) by Shiba (Prog. Theor. Phys. 46, 1971, 77) as L(E) = (E-Σ(E)) /Γ(E) . The average Green's function with Σ (E) and Γ (E) , is self-consistently determined. The obtained CPA equations were applied to a 3dim. bulk system with a simple band structure and also to quantum well systems.
2. Local atomic configurations of GaInNAsSb alloys has been investigated using extended X-ray absorption fine structure spectroscopy. Due to its small composition of Sb, there was a difficulty in the analysis of the experimental data. Upgrading the background removable technique, the difficulty has been successfully solved. A first trial of a prediction of Raman scattering simulation has been also investigated using ab initio calculations. The results quantatively agree well with the experimental results.
3. Luminescence properties of In_xGa_<1-x> multiple quantum wells with [0001], <11-2-2>, <11-20> orientation were studied for the variety of indium composition x and photo excitation intensity. For a sample with relatively large composition x, besides a characteristic red emission from the well structures, an additional emission band appeared remarkably around blue region under intensive excitation with ns-pulses into GaN band-to-band transition. The emission was tentatively attributed to the emission from defects in GaN layer induced by excess photo-carriers. It was also confirmed that both emissions decayed by a few microseconds after pulses, however, no transient ESR signal had been found.
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Research Products
(4 results)
