Carrier-induced refractive index change and optical absorption in wurtzite InN and GaN: Full-band approach

Article

关键词: QUANTUM-WELL LASERS;    ATOMIC LAYER EPITAXY;    MANY-BODY THEORY;    SEMICONDUCTOR-LASERS;    DIELECTRIC FUNCTION;    THIN-FILMS;    MU-M;    PHOTOLUMINESCENCE;    RENORMALIZATION;    SPECTROSCOPY;   

DOI  :  10.1103/PhysRevB.81.155206

来源: SCIE

【 摘 要 】

Based on the full band electronic structure calculations, first we consider the effect of n-type doping on the optical absorption and the refractive index in wurtzite InN and GaN. We identify quite different dielectric response in either case; while InN shows a significant shift in the absorption edge due to n-type doping, this is masked for GaN due to efficient cancellation of the Burstein-Moss effect by the band gap renormalization. Moreover, for high doping levels the intraband absorption becomes significant in InN. For energies below 1 eV, the corresponding shifts in the real parts of the dielectric function for InN and GaN are in opposite directions. Furthermore, we observe that the free-carrier plasma contribution to refractive index change becomes more important than both band filling and the band gap renormalization for electron densities above 10(19) cm(-3) in GaN, and 10(20) cm(-3) in InN. As a result of the two different characteristics mentioned above, the overall change in the refractive index due to n-type doping is much higher in InN compared to GaN, which in the former exceeds 4% for a doping of 10(19) cm(-3) at 1.55 mu m wavelength. Finally, we consider intrinsic InN under strong photoexcitation which introduces equal density of electron and holes thermalized to their respective band edges. The change in the refractive index at 1.55 mu m is observed to be similar to the n-doped case up to a carrier density of 10(20) cm(-3). However, in the photoexcited case this is now accompanied by a strong absorption in this wavelength region due to Gamma(upsilon)(5)-->Gamma(upsilon)(6) intravalence band transition. Our findings suggest that the alloy composition of In(x)Ga(1-x)N can be optimized in the indium-rich region so as to benefit from high carrier-induced refractive index change while operating in the transparency region to minimize the losses. These can have direct implications for InN-containing optical phase modulators and lasers.

【 授权许可】

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