InGaN/GaN quantum wells studied by high pressure, variable temperature, and excitation power spectroscopy

Abstract

The energies of photo-and electroluminescence transitions in In x Ga 1Ϫx N quantum wells exhibit a characteristic ''blueshift'' with increasing pumping power. This effect has been attributed either to band-tail filling, or to screening of piezoelectric fields. We have studied the pressure and temperature behavior of radiative recombination in In x Ga 1Ϫx N/GaN quantum wells with xϭ0.06, 0.10, and 0.15. We find that, although the recombination has primarily a band-to-band character, the excitation-power induced blueshift can be attributed uniquely to piezoelectric screening. Calculations of the piezoelectric field in pseudomorphic In x Ga 1Ϫx N layers agree very well with the observed Stokes redshift of the photoluminescence. The observed pressure coefficients of the photoluminescence ͑25-37 meV/GPa͒ are surprisingly low, and, so far, their magnitude can only be partially explained.

The effects of indium concentration and well-thickness on the mechanisms of radiative recombination in InxGa1−xN quantum wells

“…Over the past few years, the literature has witnessed reports of observations and arguments for two different radiative recombination mechanisms. One is based on spatial indium fluctuations [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] and the other on piezoelectric fields in the layers [13] [14] [15]. In this report, we show that in fact both mechanisms may operate in these devices, and that the engineering of the device can determine which of the two will dominate its luminescence behavior.…”

“…Quantitative structural and chemical information was extracted by a combination of Secondary Ions Mass Spectrometry (SIMS), Rutherford Back Scattering (RBS), Electron Energy Loss Spectroscopy (EELS) and HRTEM [11] [15]. The active region of sample 1 consists of a 2.5-nm thick In x Ga 1-x N layer (x=0.22 + 0.04), where x is the indium fraction on the Group III lattice sites.…”

Surface plasmon enhanced spontaneous emission rate of InGaN∕GaN quantum wells probed by time-resolved photoluminescence spectroscopy

“…4 Moreover, the enhancement of an emission rate is also very important for the development of communication technology and optical computing. However, spontaneous emission rates of InGaN-GaN QWs are usually reduced by the carrier localization effect 16,17 and the quantum confinement Stark effect, 18,19 and very difficult to enhance. There are only a few reports on the enhancement of the emission rates by reducing the piezo-electric field 20 and making photonic crystal structure.…”

“…These rates can be estimated from the relationship of k rad ͑T͒ = k PL ͑T͒ / int ͑T͒ and k non ͑T͒ = k PL ͑T͒ / ͓1− int ͑T͔͒. 18 By using k SP ͑T͒ = k PL * ͑T͒ − k PL ͑T͒, we also obtain k SP ͑T͒ of the Ag-coated sample ͓Fig. 4͑b͔͒.…”

Pressure Dependence of Optical Transitions in InGaN/GaN Multiple Quantum Wells

“…4 Recent pressure-dependent studies of the optical properties of In x Ga 1-x N/GaN QWs have found that the pressure coefficients of luminescence emission depend on QW sample structure and the In concentration. 5,6 One explanation of these results is that highly localized states, with small pressure coefficients, could be involved in the emission processes in the QWs.…”