INTERBAND CRITICAL-POINTS OF GAAS AND THEIR TEMPERATURE-DEPENDENCE
INTERBAND CRITICAL-POINTS OF GAAS AND THEIR TEMPERATURE-DEPENDENCE
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DOI：
10.1103/physrevb.35.9174
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发表时间：
1987-06-15
影响因子：
3.7
通讯作者：
CARDONA, M
中科院分区：
文献类型：
--
作者：
LAUTENSCHLAGER, P;GARRIGA, M;CARDONA, M
用扫描椭圆偏振仪测量了GaAs在20 ~ 750 K的复介电函数ε（ω）。利用二阶导数谱d2 ε（ω）/d ω 2与临界点线型的拟合，分析了在1.3- 5.5eV光子能区观察到的布里渊区Γ点附近（E0，E0 + Δ 0，E0 '）、沿着Λ方向（E1，E1 + Δ 1）和X点附近（E2）的跃迁结构. E0 '和E2临界点在整个温度范围内用二维线形拟合最好，而E1和E1 + Δ 1跃迁在室温下用洛伦兹线与带间跃迁的连续体相互作用（Fano线形）拟合最好.在几种理论方法中讨论了E1和E1 + Δ 1跃迁的激子特征。实验结果表明，在室温下，局域洛伦兹相互作用的连续是占主导地位的，而在更高的温度下的二维货车霍韦奇异性的修改，由于电子-空穴的吸引扰动是一个更好的描述的测量。对于所有的临界点，能量随着温度的升高而降低，而加宽增加。这种对温度的依赖性进行了分析的平均声子频率，导致重整化的能量和加宽的带隙。
The complex dielectric function ε (ω) of GaAs was measured from 20 to 750 K with a scanning rotating-analyzer ellipsometer. The structures observed in the 1.3–5.5-eV photon-energy region, attributed to transitions near the Γ point of the Brillouin zone (E 0, E 0+ Δ 0, E 0’), along the Λ direction (E 1, E 1+ Δ 1), and near the X point (E 2), are analyzed by fitting the second-derivative spectrum d 2 ε (ω)/d ω 2 to analytic critical-point line shapes. The E 0’and E 2 critical points are best fitted in the whole temperature region by a two-dimensional line shape, whereas the E 1 and E 1+ Δ 1 transitions are best fitted up to room temperature by a Lorentzian interacting with a continuum of interband transitions (Fano line shape). The excitonic character of the E 1 and E 1+ Δ 1 transitions is discussed within several theoretical approaches. The experiments indicate that up to room temperature the localized Lorentzian interacting with the continuum is dominant, whereas at higher temperatures the modification of the two-dimensional Van Hove singularity due to the electron-hole attractive perturbation is a better description of the measurements. For all critical points, the energy decreases with increasing temperature while the broadening increases. This dependence on temperature is analyzed in terms of averaged phonon frequencies which cause a renormalization of the energies and a broadening of the band gaps.