Optical transitions in InxGa1−xN alloys grown by metalorganic chemical vapor deposition

Abstract

We present the results of optical studies of InxGa1−xN alloys (0<x<0.2) grown by metalorganic chemical vapor deposition on top of thick GaN epitaxial layers with sapphire as substrates. Photoluminescence (PL) and photoreflectance measurements were performed at various temperatures to determine the band gap and its variation as a function of temperature for samples with different indium concentrations. Carrier recombination dynamics in the alloy samples were studied using time-resolved luminescence spectroscopy. While the measured decay time for the alloy near-band-edge PL emissions was observed to be generally around a few hundred picoseconds at 10 K, it was found that the decay time decreased rapidly as the sample temperatures increased. This indicates a strong influence of temperature on the processes of trapping and recombination of excited carriers at impurities and defects in the InGaN alloys.

Stokes Shift and Band Gap Bowing in InxGa1-xN (0.060 ≤ x ≤ 0.105) Grown by Metalorganic Vapour Phase Epitaxy

“…Our measured values of the band gap were somewhat lower than the ones obtained by OA. This difference is to be expected, since the PL peak energies of thick InGaN layers are typically lower than the band gap energies [28]. The comparison between the OA and the PL allows determining the Stokes shift.…”

Electric fields in AlGaN/GaN quantum well structures

“…Also shown in Fig. 7 is the result of a subtraction of the GaN band gap temperature dependence, obtained from the Varshni empirical equation together with the fitting parameters given in [14]. For temperatures above approximately 150 K the peak photoluminescence emission energy follows the rate of the GaN band gap energy decrease, as revealed by the constant value following the subtraction of the band gap dependency.…”

Composition Dependence of the Band Gap Energy of InxGa1−xN Layers on GaN (x≤0.15) Grown by Metal-Organic Chemical Vapor Deposition

“…However, in spite of the technological importance of (InGa)N, so far published data on the composition dependence of the band gap energy of the (InGa)N alloy show significant scatter, with values for the bowing parameter ranging from 1.02 eV [2] to 3.5 eV [3]. For an accurate determination of the composition dependence of the (InGa)N band gap, the gap energy has to be derived from photoreflection (PR) [2] or spectroscopic ellipsometry (SE) [4] measurements rather than from photoluminescence (PL) data. This is because the (InGa)N near band-edge PL spectrum is Stokes-shifted relative to the band edge, leading to an underestimate of the gap energy [5].…”