Optical constants of n- and p-doped In(sub 0.66)Ga(sub 0.34)As on InP (001) including the Burstein-Moss shift: Experiment and modeling

摘要

The complex optical constants (real and imaginary components of the dielectric function and index of refraction) and absorption coefficient in the range 0.3--5.5 eV have been evaluated at 300K using spectral ellipsometry for a series of n-(5.7 (times) 10(sup 17) cm(sup (minus)3) < n < 5.5 (times) 10(sup 19) cm(sup (minus)3)) and p-(6.5 (times) 10(sup 17) cm(sup (minus)3) < p < 5.0 (times) 10(sup 10) cm(sup (minus)3)) doped relaxed In(sub 0.66) Ga(sub 0.34)As grown by metalorganic chemical vapor deposition on InP (001). The authors have observed the fundamental absorption edge, spin-orbit split E(sub 1)-R(sub 1), (E(sub 1)+(Delta)(sub 1))-R(sub 1) doublet and E(sub 2) feature. The data have been fit using a comprehensive model based on the electronic energy-band structure near critical points plus relevant excitonic and band-to-band Coulomb enhancement (BBCE) effects. The intrinsic band gap of 0.612 (+-) 0.01 eV corresponds to an In composition of 66 (+-) 1%. The Burstein- Moss (BM) shift was accounted for using a Fermi level filling factor in addition to the excitonic and BBCE terms. While for the p-type samples the BM shift exhibited only parabolic effects, the n-type samples had pronounced non- parabolicity at the highest doping level, in agreement with a bandstructure calculation. By accounting for the BBCE term the authors have obtained the binding energy, R(sub 1), of the 2D exciton associated with E(sub 1)-R(sub 1), (E(sub 1) + (Delta)(sub 1))-R(sub 1) features. Except for Holden et al. this quantity has not been obtained from any previous ellipsometric or other optical studies.