Time-resolved photoluminescence ofInxGa1−xN/

C. K. Choi

¹

,

Yong-Hwan Kwon

²

,

B. D. Little

³

et al.

Abstract

The carrier recombination dynamics in a series of In x Ga 1Ϫx N/GaN multiple quantum wells, nominally identical apart from different Si doping concentrations in the GaN barriers, was studied by time-resolved photoluminescence ͑PL͒ with excitation densities ranging from 220 nJ/cm 2 to 28 J/cm 2 at 10 K and 300 K. At early time delays and with excitation densities greater than 5 J/cm 2 , at which the strain-induced piezoelectric field is screened by both photogenerated carriers and electrons from the GaN barriers, we observe a strong In x Ga 1Ϫx N PL peak initially located ϳ60 meV below the absorption edge and well above an effective mobility edge. This peak decays quickly with an effective lifetime less than 70 ps and disappears into the extended states while it gradually redshifts. The amount of this PL peak redshift decreases with increasing Si doping in the GaN barriers, suggesting that the peak is due to radiative recombination of free excitons in the screened piezoelectric field.

Influence of quantum well inhomogeneities on absorption, spontaneous emission, photoluminescence decay time, and lasing in polar InGaN quantum wells emitting in the blue-green spectral region

“…2(a)] was obtained at the assumption that the built-in electric field inside the QW system results from the piezoelectric and spontaneous polarizations in this system [15,16] with the appropriate periodic boundary conditions [28] (this situation is characterized by a step-like difference in the total polarization at QW interfaces P ). It should be noted that the internal electric field, which results from polarization effects, can be partially screened in our samples because of Si doping in InGaN barriers [29][30][31]. It means that the real built-in electric field is smaller than the electric field corresponding to 100 % P in Fig.…”

“…where c 31 and a c z are the hydrostatic deformation potentials. ε z is the strain which is defined as ε z = (c −c 0 )/c 0 , where c is the lattice constant of the free-strained crystal (InGaN in this case) and c 0 is the lattice constant of the substrate (GaN).…”

Mechanisms for photon-emission enhancement with silicon doping in InGaN/GaN quantum-well structures

“…The blueshift (73 meV at 10 K) of the PL peak in sample B compared with the undoped sample (A) has been widely observed. [3][4][5] The PL peaks of the well-doped sample (C) approximately coincide with those of the undoped sample (A), except the small redshifts below 80 K and above 200 K. All the curves in Fig. 4 show S-shaped variations of the PL peak, which is typical behavior of such clustered and strained structures.…”

“…Typically, with increasing silicon-doping concentration, particularly doping in barriers, the following phenomena were observed: (1) the photoluminescence (PL) peak blue shifted, (2) the Stokes shift (SS) decreased, (3) the PL decay time reduced, and (4) the PL intensity increased. [1][2][3][4][5][6] Such variations in optical properties were usually attributed to the screening of the quantum-confined Stark effect (QCSE) [3][4][5] because of the doped carriers. In other words, the piezoelectric field was effectively reduced with silicon doping through carrier screening.…”

Fabrication of Mesa Shaped InGaN-Based Light-Emitting Diodes Through a Photoelectrochemical Process

“…4. Choi et al 28 reported that the main PL peak blue-shift phenomenon increased with increased excitation density, mostly due to the filling of the band by the photogenerated carriers. When the laser spots were focused on the mesa-edge region in the CSS-LED samples, the PL peak wavelengths varied from 464.2 nm (1 mW) to 453.4 nm (37 mW) with a 10.8-nm blue-shift wavelength, and they mostly stayed constant at 453.4 nm when the excited laser power was increased to more than 25 mW.…”