Photoluminescence characteristic of as-grown and thermally annealed n-and p-type modulation-doped Ga(0.68)In(0.32)N(x)AS(1-x)/GaAs quantum well structures

Abstract

The electronic band structure of n- and p-type modulation-doped Ga0.68In0.32NyAs1-y/GaAs (y=0, 0.9, 1.2, 1.7) quantum well is calculated using the 10 band k.p model and the finite element method for valance band (VB) and band anti-crossing model for conduction band. Experimental characterization has been carried out temperature dependent photoluminescence (PL) measurements at room temperature. It is determined that optical transition occurs between the first quantized energy level in the conduction band (CB) and VB for n-type samples. While it occurs between localized level and VB, due to empty of the localized level closes CB for p-type samples. It is observed that the intensity of PL emission is higher for p-type samples and the effective bandgap energy redshifts with increasing Nitrogen (N) concentration. Rapid thermal annealing improves the optical quality and causes a blueshift effect. We have determined a similar amount of the blueshift for n-type N-free and N-containing samples, which may be the interdiffusion of the In/Ga atoms. The temperature dependency of the bandgap energies has been fitted using a semi-empirical Varshni equation. It has been observed that thermal Debye temperature and thermal expansion coefficient decreases with N. The redshift of the temperature dependence of the bandgap becomes larger as N concentration decreases. On the other hand, the annealing process causes a reduction in the temperature dependency of the bandgap for p-type samples