Temperature dependent recombination dynamics in c-plane InGaN light emitting diodes (LEDs) with different well thicknesses, 1.5, 2, and 3 nm, were investigated to determine the active region dimensionality and its effect on the internal quantum efficiencies. It was confirmed for all LEDs that the photoluminescence (PL) transients are governed by radiative recombination at low temperatures while nonradiative recombination dominates at room temperature. At photoexcited carrier densities of 3 – 4.5 x 10¹⁶ cm^-3 , the room-temperature Shockley-Read-Hall (A) and the bimolecular (B) recombination coefficients (A, B) were deduced to be (9.2x10⁷ s^-1, 8.8x10^-10 cm³s^-1), (8.5x10⁷ s^-1, 6.6x10^-10 cm³s^-1), and (6.5x10⁷ s^-1, 1.4x10^-10 cm³s^-1) for the six period 1.5, 2, and 3 nm well-width LEDs, respectively. From the temperature dependence of the radiative lifetimes, τ_rad α T^n/2, the dimensionality n of the active region was found to decrease consistently with decreasing well width. The 3 nm wide wells exhibited ~T^1.5 dependence, suggesting a three-dimensional nature, whereas the 1.5 nm wells were confirmed to be two-dimensional (~T¹) and the 2 nm wells close to being two-dimensional. We demonstrate that a combination of temperature dependent PL and time-resolved PL techniques can be used to evaluate the dimensionality as well as the quantum efficiencies of the LED active regions for a better understanding of the relationship between active-region design and the efficiency limiting processes in InGaN LEDs.

Date Published: 13 March 2015
PDF: 10 pages
Proc. SPIE 9363, Gallium Nitride Materials and Devices X, 93632U (13 March 2015); doi: 10.1117/12.2179637

Published in SPIE Proceedings Vol. 9363:
Gallium Nitride Materials and Devices X
Jen-Inn Chyi; Hiroshi Fujioka; Hadis Morkoç, Editor(s)