Nonlinear carrier recombination and transport features in highly excited InN layer

Abstract

A time‐resolved picosecond four‐wave mixing, or transient grating technique has provided novel features of non‐equilibrium carrier recombination and diffusion in wide excitation and temperature range of InN (n0 = 1.4×1018 cm–3) at interband photoexcitation (hν = 1.17 eV). Monitoring of the spatial and temporal carrier dynamics via light diffraction provided a direct way to control the dynamics of photoexcited carrier density N (i.e. integrated over the sample depth) in 5×1017 – 5×1019 cm–3 range. The determined bipolar carrier diffusion coefficient 2 cm2/s and its temperature dependence were used for numerical fitting of carrier in‐depth temporal profiles in non‐homogeneously photoexcited InN layers. The recombination rate was found strongly nonlinear: it followed the 1/τR ∝ B*(n0+N) law and was nearly independent on temperature in T = 15 – 300 K range. These features allowed us to suggest a trap‐assisted Auger recombination being the dominant recombination mechanism in InN. The modelling provided a value of trap–assisted Auger recombination coefficient B* = CTAANT = 8×10–10 cm3 s–1. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Carrier relaxation dynamics in InN investigated by femtosecond pump‐probe technique

“…2). To the best of our knowledge, this feature has never been observed before in InN as the lowest probe photon energy in previous measurements was 0.65 eV (1900 nm) [8,9]. This limit could be set by the cut-off frequency of the commercial Si and InGaAs detectors (which we overcame by frequency doubling the signal), but also it could be caused by a significant drop in ΔT/T 0 signal below the E g of a sample (see Fig.…”

“…The measurements were carried on: 1) a 2.3 μm thick InN layer (sample A) grown by radio-frequency plasma assisted molecular beam epitaxy (MBE) on a sapphire substrate using AlN and GaN buffers, with background carrier density n 0 = 1.4×10 18 cm -3 [9]; and 2) a 600 nm thick InN layer (sample B) grown on ~200 nm AlN buffer layer by MBE (n 0 = 4.7×10 18 cm -3 ) [3]. From the absorption spectra, the values of direct bandgap E g were found at 0.66 eV and 0.72 eV for samples A and B, respectively.…”

“…Up to now, InN layers suffer from the high defect and, consequently, background electron density, which impedes a determination of basic material parameters and obscures an understanding of the relaxation processes in excited InN. In particular, the recombination of excess electrons and holes is of great interest and is being extensively studied by many optical techniques like differential transmission (DT) [1][2][3], differential reflectivity (DR) [4,5], time-resolved photoluminescence (TRPL) [6,7], and light induced transient grating [8,9]. In spite of many works dedicated to the electron recombination in InN, a certain controversy remains in the reported carrier lifetime values as well as in the interpretation of the recombination mechanisms.…”

Ligth induced bleaching and absorption kinetics in highly excited InN layers

“…The inverse dependence of recombination time vs. total carrier density is similar to the contribution of radiative band-to-band recombination, but the determined B* value is an order of magnitude higher than that expected for InN (B=3×10 -11 cm 3 s -1 at 300 K [1]). Transient grating (TG) experiment also provided high value of B*= 8×10 -10 cm 3 s -1 [6]. In addition, it revealed the temperature dependence of B* atypical for the radiative recombination.…”

“…The details on numerical calculation are reported in Ref. [6]. The fitting provided the linear recombination time τ R = 1.5 ns and nonlinear recombination rate 1/τ ∝ B*(n 0 +N) with B*= 4×10 -10 cm 3 s -1 ; here n 0 and N stand for background and photoexcited carrier densities.…”